To import the GPG key used to sign the files:
wget -q -O - https://apt.rm5248.com/pub.key | sudo tee /etc/apt/trusted.gpg.d/rm5248.asc
To add to APT sources, edit your /etc/apt/sources.list OR add a new file /etc/apt/sources.list.d/rm5248.list and add a line like the following.
deb https://rm5248.jfrog.io/artifactory/rm5248-nightly bullseye main
deb https://rm5248.jfrog.io/artifactory/rm5248-release bullseye main
Note: Only Debian distributions supported at the moment. You can try with Ubuntu but your results may vary.