Oh, Android phones [versions]. Nominally open source (AOSP); but not having the proprietary Google Play Services means banking apps relying on GMS "protection" will not work, not even with the open-source microG port. So even using app stores F-Droid and from there Aurora (giving you the full range of apps) will not solve everything. Other considerations:
The last one will be nearly impossible for most users, so use an open-source contact/calendar from F-droid to minimize the chance of contact/calendar data leakage.
Always prefer open-source apps, because they can be audited. Closed source apps often contain malware that is very hard to detect in binary blobs.
For personal data, I use my own (open source)
For media, I prefer ad-free browsing with Midori, video browsing with Skytube, local videos with VLC, local images with Simple Gallery, local music with Music ("Lightweight and Material Music Player" for differentiation), and local Wikipedia with Kiwix.
For offline maps & navigation, I use OSMAnd [home] (free on F-Droid, 10€ on GPlay), which is based on openstreetmap. GPS and compass check with SatStat [home].
For communication, I prefer the long-dormant K-9 mail with OpenKeychain for PGP encryption. Chatting with Signal [apk] seems to be on the downturn (2021) due to questionable functionality [fefe] [reddit], but still better than the dreaded WhatsApp.
For banking, I am still stuck because I have not yet found a bank that just uses OATH standards (HOTP or TOTP, supported e.g. by Aegis) for TAN generation. Instead, they all seem to be stuck on their own proprietary apps. PayPal for the win?
Many Linuxers have a love-hate relationship with Android: While Linux at the core and somewhat development-supported, there are still so many restrictions that are hard to circumvent [root]. Nonetheless, I hope you enjoyed our little trip down Android road, and have a good day!EOF (Apr:2021)