This is a big part of why it's so important we support efforts like the pine phone and librem 5.
When these companies go belly up the perfectly functional devices we own shouldn't become effectively unservicable.
They need to start by having a working computer in a form of a phone that runs Android applications from Google Play, has support for 4G LTE. Until that happens, pine phone and librem are non-starters.
Is there a reason they can't? I'd imagine it'd have to do with NDAs and such, but the actual modified software that they wrote should be fine, right?
In my experience it is 99% of the internal politics and 1% of the legal. People in software related business ( including software engineers ) like talking about open source, GPL, etc the same way as think tanks like talking about eradicating poverty and homelessness, but any attempt to actually do something about it (release the source, build a few shelters, hire janitors) results in massive hand waving rather than action.