I did a fresh install of MacOS Catalina on my Mac Desktop. Now, when I try to install MailHub, I get an error stating "Mailhub can't be installed on this disk. This software is not supported on your system." To get around this, I moved the Mailhub app from my Macbook into the Applications folder, and moved the MailHub.mailbundle directly into the Library folder at the same location. Now, I get an error that stating "Mail has disabled the following plug-ins: Mailhub.Mailbundle. Contact the makers of these plug-ins for verstions that are compatible with Mail 13.0."
I did not realize that MailHub was not supported on Catalina and would appreciate it if you could please release a compatible version. If you like, I would be willing to beta test it for you.