as @zie mentioned, 20.09 Blockers · GitHub is what you want to look at. Really, [20.09] plasma5: printer dialog not working · Issue #98536 · NixOS/nixpkgs · GitHub is the only remaining blocking item, everything else is just a few hours of work before the final cut.
I took time off today to try and remedy the remaining plasma issue, as that’s our primary DE for the graphical installer iso, and I would like that to work well for users. It’s not a hard blocker as there is a work around using the underlying CUPS service here: [20.09] plasma5: printer dialog not working · Issue #98536 · NixOS/nixpkgs · GitHub . However, I would says that it’s not a particularly great experience, and having a more native feel would go a long way for “polish”.
There’s not much other than that. I do need to get in contact with @garbas to coordinate around the changes to the website.
You are free to use the release-20.09 channel/branch; unless there’s a valid security or usability reason, the packages should remain stable.