I want to buy a mobile phone that would be great for linux mobile (ubuntu touch or postmarket os), fairphone 4 would be almost ideal if it wasn't so big (i'm currently using pixel 8 + GrapheneOS). What do you recommend for my desire to use a compact mobile for linux + a solid camera? Thanks for the answers.
Not that many compact phones right now in general. Sub-6" is a dying breed and anything sub-5.5" is almost gone. Best bet would be some older phones but they'll all struggle with the modern web and android apps.
A solid camera narrows your choice down to Ubuntu Touch. Ubuntu Touch uses a compatibility layer for accessing Android drivers and firmware which PostmarketOS strongly discourages, so the absolute majority of pmOS ports have no working camera at all due to a lot of technical difficulties.
So for now look at what supported devices UBPorts has to offer.