I use a derivative
Without Ubuntu Pro subscription the entire Universe repository does not receive any security updates by Canonical:
canonical.com/…/ubuntu-pro-enhanced-security-and-…
You should consider switching to an entirely independent distribution that does not lock security updates behind a paywall, perhaps something based directly on Debian or Fedora.
@grue @woelkchen maybe try KDE Neon or SparkyLinux... 🤔
You can also use stable debian but enable surgically testing repos for KDE packages. 🤔
SparkyIinux would be your best option to avoid completely Ubuntu even as a low level basis. Otherwise Neon would be an intetesting option.
The day when Neon switches to Debian I break open a bottle of... i dont know yet but definitely something nice. 😁