Firstly, I had the same problem as Atlantis Installation Failure. There was /home, /boot btrfs partitions that i don’t want to format and a new btrfs for the system. The solution says it works if not making separate /home partition (and it worked for me later), but I also wanted separate /boot.
When I install only / and /boot on separate empty partitions, it gives the same error. But if / partition is Empty and /boot was created by previous distro, there is another error message
Installation Failed: External command finished with errors.
Command systemd-machine-id-setup finished with exit code 127.
/usr/sbin/chroot: failed to run command ‘systemd-machine-id-setup’: No such file or directory