Hi Henrik
Thanks for the quick answer.
Indeed there was the network-permissions extension installed.
When uninstalling the extension also the main app was uninstalled. But as there were no flows installed ...
After reinstaling the app the app now starts again.
(Side note:
On my Pixel 7a I observed that automate was also deinstalled without me doing this. Fortunately I had made a backup for my flows. ;-) )