I noticed 2 other issues with Ubuntu Mate 20.04, and installed LinuxMint Mate 20 Beta and eh voila, there are the same issues
- The My Weather Indicator doesn't keep the setting to start with the system. Looking at the crash report in Ubuntu Mate 20.04, it says there is no entry to run as a start app in Ubuntu. In Linux Mint Mate, the app causes no crash, but has got the same issue.
- The distance of the last icon in a new panel to the second icon from the bottom is always smaller in Ubuntu Mate 20.04 and Linux Mint 20 Beta. I assume it's the Mate desktop that causes the (minor) problem.