Spanish hit the other languages hard but after the dictatorship things got a lot better. Catalan is the official language of the region. I recently met several mostly Castilian speakers from Catalonia and they told me that they all understood Catalan. Whether they spoke it or not was another man. A young man there was a native speaker.
Basque is actually doing quite well. I think ~20% of the population are native speakers and there are quite a few second language speakers. There are Basque schools, Basque media, Basque signage, on and on. I recently met a young college aged man who was a Basque native speaker. Quite a few children are still being brought up in Basque. I am not sure if there are any Basque monolinguals left.
Native Catalan speakers might be ~35% of the population, and many children are still being brought up in Catalan. There are Catalan schools, Catalan media, Catalan as an official language in the government, etc. There is a huge pool of Catalan second-language speakers. There are probably not any Catalan monolinguals left, but if there are, it is an old lady in a tiny village in the mountains.
There is a form of Catalan spoken in La Franga and the Strip in Aragon that speakers say is a separate language. There are regular calls to have it recognized. However, in spite of the fact that speakers say that they speak a separate language, Catalan speakers say they can understand it just fine.
I think it is called Chapurillo a variation on the term churro, etc. which means more or less broken Spanish or bad Spanish. Many of the languages above are called churros or chapurros, and many Spaniards think they are just forms of broken Spanish spoken by poorly educated people.
Even speakers of these languages often think that they simply speak broken Spanish or bad Spanish, are often ashamed of their speech, and refuse to speak it. Speaking churro also implies ignorance, rural residence, poverty, lack of intelligence, etc.
There is dialect called Churro spoken in this same region around La Franja. It is probably the most diverse Castilian dialect in Spain. It seems to be a form of Aragonese Spanish with a lot of Catalan or Valencian mixed in.
Valencian is spoken in Valencia and the Valencian speakers insist that they speak a different language from Catalan although there is 94% intelligibility between the two. Catalan speakers do not want to break up the language and refuse to recognize Valencian as a separate language.
There is an Institute of the Valencian Language, an official orthography, etc. In particular, Valencians reject the Catalan orthography as they say it does not suit the language that the speak. ~20% of Valencians speak Valencian. It is in much worse shape than Catalan.
There is a form of Catalan that is spoken on the Mallorca Islands in three different dialects. Some have difficult intelligibility with Catalan, and they are probably closer to Valencian. Whether these qualify as separate languages is not known. Mallorcan is one of these dialects of Catalan.
There are forms of speech spoken on the border of Catalonia and Aragon in the very high mountains that are definitely not Catalan and probably not Aragonese. However, the official language institutes of Catalan and Aragon both claim these speech forms. One is called Benasquesque. This is a very remote mountain region. Whether this is a form of Catalan, a form of Aragonese or a separate language altogether it not known. It’s obviously Catalan-Aragonese transitional.
Murcian, spoken in Murcia, is mostly a Spanish dialect called Murcian Spanish, albeit quite a strange one. There are regular calls to have it recognized as an official language, but they go nowhere. However there is a hard form of it called Panocho spoken in the remote mountains in Eastern Murcia that cannot be understood outside the region. Andalusians cannot understand it either. It is probably a separate language. It has 6,000 speakers.
Mantegno spoken in La Mancha is part of a “Southern Castilian” that ranges to Andalucian. When Mantegno speakers go to Madrid, they say they are not understood. This is probably also a separate language. When spoken in rapid speech, intelligibility even with Andalucian Spanish/Extremaduran Spanish is 50%.
Andalusian is mostly a Spanish dialect albeit an extremely divergent one. However, there are a few villages in the mountains where a hard Andalucian is spoken that is not intelligible even to other Andalusian.
Aragonese is still spoken in Aragon. It is not fully intelligible with Castilian, and it is a separate language. This region was under the crown of Aragon, hence a different speech evolved here. It sounds a lot like Spanish. There are 30,000 Aragonese speakers.
It is an official language in the state of Aragon but Spain refuses to recognize it. It was formerly spoken in three forms like Extremaduran, and like that language, only the remote northern form survives. Otherwise Southern and Central Aragonese turned into dialects of Spanish, Aragonese Spanish.
Aragonese is spoken in the very high mountains of the Pyrenees in villages that are often almost totally depopulated. There are still children being brought up in Aragonese though, especially around the Benasquesque-speaking region. The children show up at school as Aragonese monolinguals.
Extremaduran is still spoken in Extremadura by 100,000 speakers. It is a highly Castillianized form of Eastern Leonese that got cut off from the rest of Leonese 400-500 years ago. Otherwise Eastern Leonese is nearly extinct. It is spoken in the mountains in tiny depopulating villages which is where it originated.
I know a Spanish speaker who actually grew up in the region, has been hearing Extremaduran all his life, and he can only understand 17% of it. The accent is wild. There is much confusion as Extremaduran is also called Castuo, and Extremaduran is the northern form of Castuo from the mountains that survived while Southern and Central Castuo turned into dialects of Spanish.
However there may be some “Extremaduran” spoken in the south too, as my friend has a word list from a tiny village in Bajadoz, and he said he could only understand 50% of the lexicon. This may be some far southern form of Extremaduran. Southern and Central Castuo is just a Spanish dialect, albeit an odd one, but it is heavily spoken and often confused with Extremaduran because people refer to both by the same term. Extremaduran is an official language in Extremadura, but Spain refuses to recognize it.
strong>Oliveno is spoken on the border of Portugal, but it’s not Portuguese. It still has ~3,000 speakers. It is spoken in a single village. Officials refuse to recognize this language, and Portugal says it is just Portuguese. It is a sort of heavily Castillianized Portuguese. Portuguese speakers say they can’t understand a word of Oliveno.
Asturian is still very much alive although it is not an official language of Spain. It is an official language of the state of Asturias. ~20% of Asturians speak Asturian and I believe there are children still being brought up in Asturian.
Leonese is the same language as Asturian spoken to the south and is in much worse shape. It is also not an official language of Spain but it is an official language of Castille and Leon where it is spoken. Amazingly, there are still Leonese monolinguals in the high mountains in Northwestern Castille and Leon.
Leonese was their first language and they learned Spanish in school but subsequently forgot Spanish and now speak only Leonese. There are still children being brought up in Leonese in the tiny depopulated villages in the mountains of Southeastern Castille and Leon near the Portuguese border. This form of Leonese is often called Porteno, and it is quite close to the Mirandese language spoken in Portugal.
There is actually a language called Eonavian/Ibino spoken between Asturian/Leonese and Galician. It is a completely separate language but no one will recognize it as such. It is closer to Galician but it is not Galician. There are still native speakers of Ibino, not sure about Eonavian.
Galician is still doing quite well. ~35% of the population of Galicia speak Galician. Almost all also speak Castilian. It is an official language of Galicia and Spain. There are Galician schools. There is some Galician media but not nearly enough. You hear Galician a lot more in the rural areas than in the big cities.
A very Castillianized Official Galician is used in the media, and it has high intelligibility with Spanish of 78%. A much harder Galician is spoken in the villages in the mountains where intelligibility with Spanish is as low as 40%. The form of Galician spoken in the far south on the border with Portugal is not intelligible with Portuguese or the rest of Galician and is not spoken outside the region. It is actually a separate language though no one will recognize it.
Rio de Onoro is a village on the Portuguese border. Rio de Onorese is still spoken, though everyone thinks it is extinct. It is a form of Mirandese spoken in Spain and should be recognized.
Cantabrian is said to be a form of Spanish, but actually it is part of Extremaduran. Extremaduran is nothing less than Eastern Leonese and Far Eastern Asturian that started going over to a form of Old Spanish ~500 years ago. Asturian-Leonese survived in the coastal mountains and in the mountains of Extremadura to the far south, but the rest of it mostly went extinct. Today Eastern Leonese is just about dead.
But Extremaduran speakers say if they go to Cantabria, everyone understands them, and it sounds like they are speaking the same language. These same speakers say that if they go to Oviedo in Central Asturias where people speak Asturian and speak Extremaduran, they are not understood. Therefore Extremaduran and Asturian-Leonese are two different languages, and Cantabrian, instead of being a Spanish dialect, is part of Extremaduran.
Some Cantabrian speakers held out for a long time in the rugged mountainous province where some areas are still reachable only on foot or maybe by donkey. One speaker said his recently deceased grandmother was a Cantabrian monolingual who died in the last 20 years. She had stubbornly refused to learn Spanish as she considered it to be “an imposed language.”
Formerly there was a separate language called Montanes spoken in the mountains, while Cantabrian was spoken on the coast. Half a century ago, they could not understand each other. But now with leveling, the people in the mountains understand the people on the coast just fine.
There are reports that Cantabrian may be going out in Cantabria. But Cantabrian is still spoken and it is children are still being brought up as Cantabrian monolinguals. In the mountains, the children all show up at school speaking only Cantabrian, and the teachers can’t understand the students.