Switch:

rm -f /etc/apt/sources.list.d/pve-enterprise.list
rm -f /etc/apt/sources.list.d/pve-enterprise.sources
rm -f /etc/apt/sources.list.d/ceph.list
rm -f /etc/apt/sources.list.d/ceph.sources
echo "deb http://download.proxmox.com/debian/pve trixie pve-no-subscription" > /etc/apt/sources.list.d/pve-no-subscription.list
echo "deb http://download.proxmox.com/debian/ceph-squid trixie no-subscription" > /etc/apt/sources.list.d/ceph.list
apt update
apt-get dist-upgrade

Remove nag:

cp /usr/share/javascript/proxmox-widget-toolkit/proxmoxlib.js /usr/share/javascript/proxmox-widget-toolkit/proxmoxlib.js.bak
python3 -c "
import re
f = open('/usr/share/javascript/proxmox-widget-toolkit/proxmoxlib.js', 'r')
content = f.read()
f.close()
content = re.sub(r'res === null \|\|\s+res === undefined \|\|\s+!res \|\|\s+res\.data\.status\.toLowerCase\(\) !== .active.', 'false', content)
f = open('/usr/share/javascript/proxmox-widget-toolkit/proxmoxlib.js', 'w')
f.write(content)
f.close()
print('Done')
"
systemctl restart pveproxy