There was once a time when I would press the spacebar on a tex file in the Finder and I would see a Quicklook preview of it using the theme I used when TextMate is open, complete with syntax highlighting, etc.
I'm not sure what I did, but now when I press the space bar, I see only a picture of the document icon with the TextMate logo on it. It does correctly label it "TeX" with that capitalization, though.
To experiment a little, I deleted the line <string>tex</string> in the TextMate.app Info.plist. Quicklook now works on tex files, but it looks like it's using the built in macOS ql plugin for plain text. That is, it's not using the default TM theme and thus there isn't any syntax highlighting, etc.
When I put back <string>tex</string> in Info.plist and then do touch TextMate.app, it goes back to the preview of the document icon as before.
I don't mind the Quicklook preview without the theme colors, but it would be nice to restore TextMate's Quicklook, if possible.
I'm using TM 2.0.17 on macOS 10.15.7.
Best wishes, Anthony