Just upgraded to 22.04 and the ebook viewer is unable to open .mobi file with ebook viewer error message:
calibre, version 5.41.0
ERROR: Render process crashed:
The Qt WebEngine Render process has crashed.
You should try restarting the viewer.
I've tried this before and after Calibre update and is getting the same result.
Bug report filed
as recommended by @andrew.46, using the repository version will resolve the problem. Kindly scroll down to view his answer for a complete walk-thru.