A: By the time I wrote those scripts free5GC was tested by its developers in Ubuntu Server 20.04.6 (see this snapshot). Another point to consider is that, the kernel version officially supported by the GTP-U module is 5.4.x (which comes by default on Ubuntu 20.04.x). On top of that, newer kernel versions (like 5.1x and 6.2) had some glitches (for example, see those issues here and here) and Ubuntu 22.04 faced some hiccups (example here)
A: As mentioned on a message on its official blog and on the release cycle page, Ubuntu 20.04 will be supported until April 2025 which gives some time for free5GC's developers to update/adapt/test the project (and its dependencies) on the new 22.04 LTS release.
Q3: The minimum requirements reported by your script are quite lower than the ones on the free5GC's official documentation. Why?
A: The requirements from there (available on this page) were designed to work in a production grade environment where 5G devices would connect, etc. My target environment is a testing one with only a small number of simulated devices connected. Because of that, I've tried to scale down the requirements as much as possible. Anyway, the machine where the scripts will run may be adapted to your preferences, the amount of RAM and CPU power available will affect the time required to build the software (e.g. free5GC NFs, UERANSIM...), the number of connected devices and the general performance of the environment.
A: No, I don't. Specially if a stable environment is required (see FAQ #1). Support for this Ubuntu version was added just to test newer versions of the kernel and free5GC's support for Ubuntu 22.04.
A: Currently, kernel 5.15.x, more specifically 5.15.0-116-generic. If a newer kernel is a requirement (e.g. to use MPTCP), perhaps you may use this version on an Ubuntu 20.04 installation.