Am I missing something?  On my old laptop, running Mojave, on which I've been upgrading TM forever, I QL any file TM recognizes and the OS uses TM's parser, I get my theme, etc.

On my shiny new Catalina laptop, I get what I think is the built-in basic text QL plugin, no TM.

It's been a while, I admit... is there something somewhere that has to be turned on?