I tend to think in terms of using the one RPF supported OS - Raspbian, for which there's no problem with kernels/modules. I've never proposed trying to boot other OS's via an SD card
I like to have one SSD with all my data but switch between operating systems. I've been doing that for over 20 years and obviously that creates a few problems with Linux, because mixing desktop environments, while using different /root partitions sometimes creates minor havoc. For example one machine with separate XFCE, Kubuntu, LXDE and Gnome root partitions, all with their own programs, sharing a single /home, and often sharing the programs' config files there - all for different environments (and different update levels).
At the moment I'm running Raspbian with a lot of XFCE bits in it. Plus all my weird homebrew stuff.
I suspect though, that RonR's boot system might be able to let me start things the way GRUB does in my bigger machines.
I really must explore it more. But I have a couple of questions before I find time to dig into it.
Is it restricted to USB boot, or can it be used from microSD to boot to /root file systems on various USB devices which share /home stuff on SSD.
Or is that what NOOBS is for.
Or, would it be better used the way I use GRUB, targeting separate /root for each environment, while sharing a common /home