Having reinstalled my Promox nodes a few times due to tinkering with various things. One of the most annyoying things that comes back when a node gets reinstalled is the subscription banner. Really easy to disable it, following the below steps:

If you have not installed vim on your nodes might want to:

apt install vim

cp /usr/share/javascript/proxmox-widget-toolkit/proxmoxlib.js  /usr/share/javascript/proxmox-widget-toolkit/proxmoxlib.js.bak && vim  /usr/share/javascript/proxmox-widget-toolkit/proxmoxlib.js

Find the following block:

Ext.Msg.show({
 title: gettext('No valid subscription'),

Searching in vim is done by opening the file and pressing /, in our case:

/Ext.Msg.show

Replace Ext.Msg.show with void:

void({
 title: gettext('No valid subscription'),

Restart pveproxy.service:

systemctl restart pveproxy.service