From Django 4.0, form rendering is now fully template based. It’s new, so the patterns are still to be worked out, and no doubt there’s room for better documentation, but…
If you were to set Form.default_renderer you could provide your own renderer that implemented get_template() to look in the correct directory for your form type.
… I think 
— It should work, but I’ve not done that (yet) myself, and you’ll need to play. It would be interesting to see what you come up with if you get it working, or what issues you hit if you don’t.
// cc. @smithdc1
HTH.