I think the problem is the adoption that a server administrator can only install Ubuntu 16.04 LTS and then Ubuntu 20.04 LTS because oft the support time from Ubuntu 16.04 LTS till April 2021.
I think it is not possible to dist-upgrade directly from 16.04 LTS to 20.04 LTS. Normal administrators do also not reinstall all from 16.04 LTS to 20.04 LTS betweeen April 2020 and April 2021 (end of support 16.04 LTS).
If someone uses an Ubuntu 16.04 LTS - server he/she should dist-upgrade to 18.04 LTS betweeen April 2018 and April 2020 and dist-upgrade to 20.04 LTS between April 2020 and April 2021. And then there shoud no problems with apache2, mariadb, php and nextcloud versions.
Normal administrators do not cancel an ubuntu lts release because of longer support time of the older ubuntu release.
For longer release times use CentOS.
https://wiki.ubuntu.com/Releases
https://www.debian.org/releases