I was out of town for a while, but recently I could try out the new Armbian release v25.8.1, which incorporates the changes made by Ryzer. I chose kernel version 6.15 and did get an HDMI output on a Dell 21,5" monitor. So I managed to configure the pcduino2 for its purpose and I am using it again after many years. Excellent! Thank you so much for all your efforts! Great to be back as an Armbian user.
Just as a side note: I was first trying with my Dell UltraSharp 34" monitor and there the HDMI output still does not work. I does work with the old Armbian 5.38 version for pcduino2 from the archives and also with Raspberry Pi 3 using a recent version of Raspberry Pi OS. Anyway, this is just for information. I do not think it is worth investigating this issue.
pcduino2user got a reaction from Ryzer in Trying Pcduino2 on a newer kernel