well based on the info on their site, you have no support/help except what you can get on the forum.
and believe me their forum suck big time, just like their devs attitude.
also, if you do update from the no-subscription repo you are risking of screwing up the install as per their warning
no-subscription server code is not as thoroughly QAed as Enterprise server code. so you might get a lemon from there.
functionality wies everything should work though.
PS: also if you want to remove the nag screen
you can run "sed -i "s/data.status !== 'Active'/false/g" /usr/share/pve-manager/ext6/pvemanagerlib.js"
after install. you will need to rerun it after upgrades or major updates as the file can be overwritten.