bitcoin-qt starts fine and shows the GUI. After some period, the GUI disappears. There seems to be no way to restart it unless I kill the bitcoin-qt process and restart it. System information is in the attached txt file. TLDR; Linux Mint (20.2) Cinnamon (5.0.5) with kernel 5.11.0-25-generic. I would be happy with a command line option that causes the GUI to restart.
If I have the GUI’s Information window showing, it does not disappear. Just the main (wallet) window disappears.