They've been around for a 3 years, which is not a very long time for FOSS. However the software seems stable, fast, it has lots of releases, all of which are good signs in terms of future availability.
I forgot the name, but there is a software "law" that software that has been around for N years will probably be around for N more years (so the longer it's been around, the longer it will continue to be around).
I see about 7 big contributors: https://github.com/immich-app/immich/graphs/contributors. I think most of them work for/are sponsored by FUTO: https://futo.org/about/what-is-futo/
And seeing the FUTO description, I like that. We need more of that :-)
> FUTO is an organization dedicated to developing, both through in-house engineering and investment, technologies that frustrate centralization and industry consolidation.
Though this part needs more research:
> From its founding, FUTO has been funded entirely by investment from its sole owner, Eron Wolf.
I have no idea who Eron Wolf is...
Edit: found some more info. Potentially promising:
https://news.ycombinator.com/item?id=35914264
https://gitlab.futo.org/eron/public/-/wikis/Thoughts-on-Open...
Though the question remains about FUTOs long term sustainability.