I had the same issue and this worked for me: -office-tools/support/mathtype-support-notices/support-notices/error-message-in-word-and-powerpoint-for-macos-in-catalina-and-big-sur-caused-by-previous-mathtype-installation.htmlEssentially the idea is to uninstall math type completely with the uninstaller that they provide.
I need ttf-mathtype fonts for work with LibreOffice Writer. I have installed it in the past and everything worked fine. I have installed LibreOffice and ttf-mathtype on other computer, but it doesn't work as it should (it doesn't work at all).
I have used: