KDE neon unstable edition is built from git master. For the last few weeks we have frozen the published repo because we knew the move to Qt 6 based builds of KDE Frameworks and Plasma would break install. They will still break install but now is the time to give it a try. It is vitally important to update your neon-settings-2 package first because the Qt 5 and 6 builds have overlapping files and this will allow that.
pkcon refresh pkcon install neon-settings-2 pkcon update
or if you prefer apt
apt update apt install neon-settings-2 apt full-upgrade
This is very early stage development. Almost everything is super broken from a user perspective, and it may not be useful to get 500 bug reports about every little thing so tread carefully. For any bug reports you do report add
Best of luck!