I use linux on nearly all my PCs / servers. I do think about moving my phone to more open platform (fairphone, or rooting phone), but I don't like phones in principle, so I do not install stuff there. I do not do things on phone.
I have my apps as web pages, so I access them from phone web browser. I do not care about phone apps that much.
I use fdroid for calendar, gallery, and music though.