Thank you for your input, that was very useful.
My main problem now is using steam in Leap 16. This is my main box (the fastest CPU and GPU), and I’d like to keep using Steam on it. I installed Steam in Thumbleweed (no flatpak) without issues, but I understand TW is not for (my) production.
This box dual-boot with windos10 (on extended support), and I had Steam on it on Leap 15.6 for a couple of games that won’t run on linux (or at least they didn’t, I haven’t checked recently), but after some woes I’ve been unable to install Steam (see Nvidia + Steam 32 bit woes after system reinstall ).
I could use w10 for all steam games, but this box is also a linux media server that my wife sometimes use while I’m gaming.
So that’s a conundrum for me 
I’m aware that I’ll have to let go of Yast (from my dead, blackened hands), but really, agama’s partitioner is not good enough for dealing with all want-to-keep partitions in this box, including efi and windows. At least that was my perception when I tried to install Leap 16.0 on this box. Oh well…