>So the UEFI system is able to read mdraid 1.2 too, and can access ESPs inside of it?
Yes, currently install & boot with mdraid 1.2 works for other OS like CentOS etc.
Ubuntu subiquity installer seems to be blocking it for ESP/Boot-device. Ubuntu legacy debian installer was allowing md-raid disk to be selected as Installation destination (including ESP), however we were facing grub install error during installation as in https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1776685 and https://bugs.launchpad.net/ubuntu/+source/grub-installer/+bug/1466150
>So the UEFI system is able to read mdraid 1.2 too, and can access ESPs inside of it?
Yes, currently install & boot with mdraid 1.2 works for other OS like CentOS etc.
Ubuntu subiquity installer seems to be blocking it for ESP/Boot-device. /bugs.launchpad .net/ubuntu/ +source/ grub2/+ bug/1776685 and https:/ /bugs.launchpad .net/ubuntu/ +source/ grub-installer/ +bug/1466150
Ubuntu legacy debian installer was allowing md-raid disk to be selected as Installation destination (including ESP), however we were facing grub install error during installation as in https:/