Unlike the above post, I don't want this for tax purposes etc., but rather just to understand where all my distance driven comes from.
Edit: I've done some more research and haven't found anything, for now I'll just use an OnlyOffice spreadsheet. If I find the time, I might try developing an app for this at some point.
Edit 2: After developing my app for a week and then showing it to a friend, he instantly found exactly what I was working on...
Imo it looks to be very bloated for what I want. I don't need (or necessarily want) a GPS track for the whole journey, but rather just start and endpoint. I intend to tell the distance from my cars odometer.
Also I already started making my own app by now anyway and I'm far too committed to consider other options lol
Use an automation app like Automate, Macrodroid, Tasker.
I have a few scripts that respond to geolocations, but it wouldn't be hard to add some other features.
Currently these scripts save output to a text file (CSV) that is synced to my file server using Syncthing.
You could use various triggering mechanisms, such as BT connect in the car, or an NFC tag, disconnecting, from wifi (that's a good indicator you're traveling), etc.
There's also a location tracking app you can self host, let me find a link.