Nice post, I would add a couple of points re. Welsh. The first is that it was not really dead 50 years ago. It got as low as 15% of the population in the 50s/60s, and was undoubtedly headed for obscurity and ‘death’, until the revival, as you mentioned. But it was still alive (q.v. Dafydd Iwan’s [0] most famous song, “Yma o Hyd”). Now welsh is spoken by around 18% of adults and 25% of children, and is increasingly seen as an important part of modern Wales.

The other important thing to realize is that Welsh was ‘formalized’ in 1620 when the Bible was translated into it[1]. This had the double effect of unifying the distinct regional dialects into ‘high Welsh’ (a distinction which exists to this day!) but also, crucially, providing a standard text which people could use to learn to read and write. It meant that Welsh was able to flourish into a full legal language, and not just used as a ‘home’ language.

This gave it a backbone which was not present in other ‘regional’ languages (such as its nearest relation, Cornish), which in turn have all but died out.

With respect to the original post, I note that the Bible was only translated into Occitan in the modern era [2], which would support the evidence of it still being a language only used at home, and not in formal situations.

[0] https://en.m.wikipedia.org/wiki/Dafydd_Iwan

[1] https://cy.m.wikipedia.org/wiki/Beibl

[2] https://en.m.wikipedia.org/wiki/Bible_translations_into_the_...