Hm, if you're seeing that when looking at the inspector for STM, something is very wrong... can you try a full re-import? Try doing a backup of your project (if you have custom Text Data files, these can be added back by putting them in the right folders and using the "Refresh Database" button I mentioned later, which should hopefully comeback once this is done...), then completely delete the SuperTextMesh folder, then re-import the asset. With any luck, settings you have on individual text objects should carry over properly. So please do this backup just in case a step gets missed or it doesn't go well, we can just try again.
I try to make the upgrade process smooth from version-to-version (in the docs, I'll list any major changes underneath the changelog), but when going past multiple versions, it's possible for things to break if the right steps aren't taken... Based on this evidence, I think some file got misplaced or not updated properly between imports?