For what it's worth, I had luck starting with Raspbian, then changing the apt sources to Debian sid (unstable) and upgrading without issues. The default Raspbia

For what it's worth, I had luck starting with Raspbian, then changing the apt sources to Debian sid (unstable) and upgrading without issues. The default Raspbian desktop environment becomes buggy, but XFCE4 works perfectly. If you want to run Debian on your Pi4, that's a pretty easy path.