Irish Gaelic, at least, is available on Duolingo. I've thought about learning it before; I listen to the music constantly and while I don't normally enjoy learning languages, this is one of the few that I feel drawn to based on its sheer beauty.

That said, I don't know how you make people care about preserving something when they seemingly just don't. Maybe you can cultivate genuine appreciation for the language, but it's no surprise that's it's easier to just use English, and I don't see very many people using it purely out of a sense of duty. Languages are natural things and their usage has to come from a natural, human motive. It's hard to prop that up artificially.

Glossika, which I use and recommend for other languages, has a free Gaelic course:

https://ai.glossika.com/language/learn-scottish-gaelic