Just noticed that OpenHAB 4.0.0 is now suggested as an upgrade with APT in Armbian. Accepting the suggested upgrade would now install OH 4.
If you are like me and want to wait for a few dot releases before you take the step to 4.0, you can use apt-mark to “freeze” your OpenHAB version at 3.4 while you still can upgrade the rest of your system
sudo apt-mark hold openhab
Should do the trick.