Ideally, all my web applications MUST support PHP 7.4 BEFORE upgrading Debian, so, to do not cause any downtime after upgrading Debian (T1306).
Unfortunately, sury.org is not available anymore for Debian buster. So, I must invent a dirty hack to give temporary support to PHP 7.4.
The goal is, upgrade Nextcloud as much as possible (e.g. T1308) so that I can then migrate Debian (T1306) without causing a Nextcloud upgrade deadlock.