$ sudo apt-add-repository -y ppa:rael-gc/rvm
Repository: 'deb https://ppa.launchpadcontent.net/rael-gc/rvm/ubuntu/ kinetic main'
Description:
RVM (http://rvm.io) is a command-line tool which allows you to easily install, manage, and work with multiple ruby environments from interpreters to sets of gems.
Please, check install instructions here: https://github.com/rvm/ubuntu_rvm
More info: https://launchpad.net/~rael-gc/+archive/ubuntu/rvm
Adding repository.
Found existing deb entry in /etc/apt/sources.list.d/rael-gc-ubuntu-rvm-kinetic.list
Adding deb entry to /etc/apt/sources.list.d/rael-gc-ubuntu-rvm-kinetic.list
Found existing deb-src entry in /etc/apt/sources.list.d/rael-gc-ubuntu-rvm-kinetic.list
Adding disabled deb-src entry to /etc/apt/sources.list.d/rael-gc-ubuntu-rvm-kinetic.list
Adding key to /etc/apt/trusted.gpg.d/rael-gc-ubuntu-rvm.gpg with fingerprint 7BE3E5681146FD4F1A40EDA28094BB14F4E3FBBE
Hit:1 http://de.archive.ubuntu.com/ubuntu kinetic InRelease
Hit:2 http://de.archive.ubuntu.com/ubuntu kinetic-updates InRelease
Hit:3 http://de.archive.ubuntu.com/ubuntu kinetic-backports InRelease
Hit:4 http://de.archive.ubuntu.com/ubuntu kinetic-security InRelease
Ign:5 https://ppa.launchpadcontent.net/rael-gc/rvm/ubuntu kinetic InRelease
Err:6 https://ppa.launchpadcontent.net/rael-gc/rvm/ubuntu kinetic Release
404 Not Found [IP: 185.125.190.52 443]
Reading package lists... Done
E: The repository 'https://ppa.launchpadcontent.net/rael-gc/rvm/ubuntu kinetic Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
Following along the README I get: