As per my understanding from the chat he is going to map both.
F1/F2/F3/F4 and 7890 for Hotbar.
6 and R for Ultimate.

If we are only going to get single mapping then I would prefer F1/F2/F3/F4 for Hotbar and keeping 6 for Ultimate.


PS: If F3 is opening Quick Find in your game window then disable the browser hotkey:
https://www.askvg.com/tip-disable-qu...zilla-firefox/
(Idealy it should not work on the game window, but it was for me)