It doesn’t look like forcing onion with HTTPS Everywhere user rule sets is possible with the current version which is 2019.5.13. Or at least it can’t be done using these instructions.
https://whonix.org/wiki/Forcing_.onion_on_Whonix.org#Adding_User_Rules
I am able to copy over my user rule sets from an earlier Tor Browser/HTTPS Everywhere version. (works OK). However, unless someone has an idea, this part of the forcing onion docs should be deprecated imo.