Boards on Desktop app lead to empty page

the desktop app on my Tuxedo notebook with Ubuntu 22.04 does no longer show the “Board” page. I have rebooted, re-installed and upgraded the app (version 5.7.0 commit e999e2c). But the problem remains.
When I click on “Boards” I get an empty page showing only the words “Redirecting to error page”. Many thanks in advance for the advice how to solve this…