Linux Phones

There's actually quite a few bits that are compatible! I tried out the OnePlus 6 with Phosh, and there are lots of good apps already! Make sure to look for apps that are labeled "adaptive" in the software store, those work the best on mobile. Firefox also works quite well with the "Add Water" app, it gives it a GTK theme (matches with Phosh) and increases padding by a bit.

As for the apps I liked (all of which adapted well in mobile): Geary (email client, GTK3 I think, so you need to enable dark mode in the mobile settings), Fractal (Matrix client), Gapless (music player), GNOME/KDE Weather, Secrets (KeePass client), Apostrophe (Markdown notes), Mimick (Immich sync client), Fotema (photo gallery), Animatch (match game with cute art and no microtransactions or ads, open-source too!), Ultimate Tic Tac Toe (actually has quite a bit of strategy involved), Pentobi (very similar to the "Blokus" board game if you've ever played that, very fun!)

And there are a lot of KDE/Qt equivalents that I have not tried (since I was running the GTK-based Phosh)

Being able to install Flathub apps was very handy actually, and it's one of the reasons why I decided to try postmarketOS over something like Ubuntu Touch.

If you want to explore other mobile apps (on Flathub): https://flathub.org/en/apps/collection/mobile/1