I installed cinnamon in Ubuntu 20.04 to give it a try.
Later I tried to uninstall from your page at >here<
‘sudo apt-get install ppa-purge’
got this message;
‘PPA to be removed: embrosyn cinnamon
Warning: Could not find package list for PPA: embrosyn cinnamon’
'sudo ppa-purge ppa:embrosyn/cinnamon ’ gave the same result.