In case anyone finds this who is also interested: I just stumbled upon an implementation of shadcn/ui components with css modules that looks pretty solid: https://github.com/qwalker8408/shadcn-css/tree/main

Hopefully something like this will be made official - at least there is some discussion going on in the shadcn/ui repo: https://github.com/shadcn-ui/ui/discussions/2832