I've used gummiboot before systemd ate it; and I've used rEFInd. Mainly, I just followed the excellent documentation @ https://www.rodsbooks.com/; that's also how I first familiarized myself with UEFI (Thanks Rod!).

My brain has leaked all the information I understood (unfortunately). Is rEFInd still active? Is there a gummiboot fork (besides systemd)?

Personally, I kind of hate Redhat calling itself that now, it's IBM. You can tell because all of the online knowledge from the community on their websites are now pay-walled. RIP Redhat (CentOS) (I'll miss you)

P.S. Thanks Rocky Linux (and others like it)

rEFInd is great! I wish they just updated the default theme to something nicer.