The earlier valid key servers are no longer available ( see: gpgkeys: HTTP fetch error 6: Could not resolve host: pool.sks-keyservers.net · Issue #5096 · rvm/rvm · GitHub ). RVM documentation is not updated by now which is why there’s no official RVM way right now (this is the documentation I’m referring to: RVM: Ruby Version Manager - Installing RVM )
However, on a CentOS 8 I found the following solution with some searching around:
gpg --keyserver keyserver.ubuntu.com --recv-key 409B6B1796C275462A1703113804BB82D39DC0E3 7D2BAF1CF37B13E2069D6956105BD0E739499BDB
I also verified this to be working right now.
Documentation fix is on the way within the next 30 minutes.
Please however note that this solution may not be correct at all.
Please use the documentation, it really is holding your hand. If you have packages installed already remove them from your command before hand.