Too bad you didn’t buy a pinephone! 
Too bad PostmarketOS (based on Linux, not on Android) has not made much progress for your device, or it would be a fun place to start. It could be anyway if you want adventure and to help make progress. Xiaomi POCO F1 (xiaomi-beryllium) - postmarketOS
LineageOS and a manual install of F-Droid is a good place to start, I agree. I would avoid microG unless you really run into something you “need” it for. microG is to LineageOS as methamphetamine is to coffee or caffeine, if you get what I mean.
I recommend you try DivestOS. It is a fork of LineageOS, without microG, but with F-Droid and privileged extension included, with a lot of other changes you can read about and mull over at your leisure. Your device is listed as Untested: Devices - DivestOS Mobile so maybe you can help make progress, and get experience with adb, logcat, etc.
You can interact here with the developer, @SkewedZeppelin : DivestOS: long term device support with enhanced privacy and security There was a little discussion of Xiaomi Poco F1 (beryllium) but apparently it still needs more testing.
Other tips: Maybe you would benefit from backing up some things from the as-received device. But who does backups?! LOL
Happy distro’ hopping!