With help from a teammate in investigating the common problem with our apps, he discovered a cure by installing the deprecated gtk2 library module. Available in the 20.04 distro.
All you need to do is to run this command:
sudo apt install appmenu-gtk2-module
and then rebooting. You need to reboot to get the new library working.
This allows older applications based on the older menu API to function normally. Solved the issue with Boinc Manager and GKrellm config menu.
Ref: https://launchpad.net/ubuntu/bionic/+package/appmenu-gtk2-module