I think the Minimum Mass Viability Metric (MMVM) for Linux on the desktop is games, while for Linux on phones it's phone calls and text messages. This doesn't mean either of them aren't viable for some groups if those needs aren't met (I used Linux on my desktop in 2014, for example), it just means that's what a mass audience would need for it to be viable in general.
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A heavily-motivated user could take a Linux phone (note: this is referring specifically to mainline and not relying on Android, not that there's anything wrong with that since every bit helps) with calling and texting support and a point-and-shoot digital camera/DSLR/film camera with them places if that phone doesn't have a good camera/doesn't have full camera support yet.
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@DrewNaylor I think there may be a bit more to it, cause we've had reliable calls and text messages for a decade and a half or so now :) (e.g. Neo Freerunner with FSO or QtMoko once bug #1024 was fixed)
@DrewNaylor It's still been there for years and the adoption did not skyrocket just because of that.
@dos I meant for newer projects that weren't from the older era but didn't mention it.