Not much help here - just saying, Bluetooth in Linux is giant pezzo di merda!
It’s my main bugbear! Just when you think stuff’s working, it stops working! And then you try and try, and do this, edit that, and it suddenly works, and it seems like black magic, and just when you’re used to it working, some bad juju pulls the rug out from under you!
I’ve got THREE Targus USB BT 4.0 dongles - same symptoms on all of them, on Ubuntu 20.04 (upgraded from 18.04) - trying to get my new BT Microsoft Surface Designer mouse working… it pairs… it works, for maybe 30 minutes, sometimes as long as two hours… but then stops… unplug the dongle… wait “X” minutes and try again - and no luck… so I give up and go back to wired mouse… and I’ll maybe try again the following day, and it will pair and work, for a bit, rinse, repeat.
I’m seriously considering buying one of those PCIe cards that also do Bluetooth (I don’t need the wifi features, this is a desktop - so I use Gbit ethernet over Cat 6 UTP). Some of these cards are just mini-pcie (i.e. laptop form factor) adaptors with a wifi / BT module…
My main local computer bits shop sells a couple of Asus branded PCIe wifi cards that also do Bluetooth, but I don’t really trust them, even when I go to Asus’ website, it won’t tell me the chipset details (this is so they change to whatever other chipset they want to switch to without any warning) - so I can’t determine if they have Linux support.
Note : I don’t use BT dongles on any of my Dell laptops - because they have onboard BT, and I don’t seem to get these symptoms… However this 20.04 desktop machine is my Synergy KVM server when I’m working at my desk (i.e. one keyboard/mouse combo to control everything)… So I want reliable bluetooth working on it.
I’m also probably going to try for something (a PCIe solution) that does Bluetooth 5.0, so I’m “future proofed”…