Running a Sony Xperia 10 III for a couple of months now, previously used SFOS on a Fairphone 2, and an N900 with Maemo before that.
Web browsing
The stock browser is not only too old, but also lacking in too many features I wouldn’t want to be without with the current state of the internet; especially addons; I’ll give a brief description of what I’m using.
Started out using Firefox years ago, when that got removed from F-Droid for having too many proprietary blobs I switched to Fennec, and lately I’ve been using Mull instead.
I’m using Mull in conjunction with the most strict settings in the browser itself, together with:
Consent-O-Matic for, opposed to “I don’t care about cookies”; it does care about cookies and kindly declines them all.
Decentraleyes; nice description of what it does with screenshots when you follow the link.
Privacy Badger
And last but certainly not least uBlock Origin
Chat
I use a FOSS and de-blobbed version of Signal called Molly FOSS which has a neat F-Droid repository.
I’m running it along side of Whisperfish, but that is lacking a few features and sometimes has issues for me, plus I cannot run it standalone (couldn’t get passed the setup process), so it’s only a linked device now.
Voicecalls
I use the Phone application, the only beef with that is that sometimes the recording doesn’t work, it corrupts the audio file, that happens about 1/3th of the times that I try to record a call.
Maps and navigation
Pure Maps in conjunction with OSM Scout Server, awesome FOSS and offline navigation.
Only beefs there is performance when looking up addresses which can take a minute or two, but I got entire Europe installed so that may be the culprit. Also I’m missing features like real time traffic information and speed cams / traps, though currently I make do without them.