The bitcoin.conf file is empty, I guess on Linux this is done through the bitcoin-qt.conf file... I've tried adding fHideTrayIcon=false to bitcoin.conf but it didn't do anything.
No, by default, bitcoin.conf
is empty, you'd need to add the option yourself. Note that bitcoin-qt.conf is a completely different and separate file and used for different things!
It's somewhat common problem if you use linux, even though usually it's annoying UI bug/glitch. Developer don't test their software across different linux distro or different DE.
I don't think it's a Bitcoin Core bug tho... as I fired up a Linux Mint Cinnamon VM and installed Bitcoin Core v0.19.1 on it... and it works fine. I can see the the minimise to tray options, they're "clickable" and function as they should:
There must be something about defa1's setup that has changed the options for the notification tray.