@christianlupus
That is not fully true. While Ubuntu 20.04 LTS and Debian 11 you can use PHP 7.4 from their repositories. But maybe Nextcloud 26 stops support PHP 7.4.
It’s a bit of the Windows XP approach. Perhaps former windows users.
A completely outdated operating system with always the latest software.
Works for many users for a decade.
You can better move to Ubuntu 22.04 LTS with PHP 8.1 than use the old Ubuntu 20.04 LTS with a newer PHP version from another source.