I've created new ISO images for FAI. Now, they install Debian 11 using kernel 5.10. The ISOs are available from
https://fai-project.org/fai-cd
There's also a Ubuntu version of the FAI CD which installs Ubuntu LTS 20.04 in two variants. A desktop and a server installation is available.
If you want to install the Debian oldstable version (Debian 10), please use the FAI.me service.