I just wanted to give a small update / summarize. I recently changed from Manjaro GNOME Edition to Manjaro KDE Edition. HighDPI scaling (fractional scaling) in X11 under KDE is working almost perfect. In GNOME I had to scale the interface with factor 2 and then scale it down factor 1,5x1,5 using xrandr --scale, which gave me some problems using auto screen rotation. I also tried the experimental scaling under GNOME wayland, but using this gives me unfortunately blurry fonts. Auto screen rotation does also work pretty well under KDE using kded_rotation as mentioned in the ArchWiki (https://wiki.archlinux.org/index.php/Tablet_PC#With_a_KDE_module).
To get the rotation order correct, the same configuration file as for GNOME has to be created:
# Acer Spin 1 SP111-32N
ACCEL_MOUNT_MATRIX=0, 1, 0; 1, 0, 0; 0, 0, 1
From the issues mentioned in my first post, only one remains:
The tablet mode is not working. Once the convertible is folded into a tablet and back, there is no way to get the keyboard / touchpad working again, than doing a reboot. To be more precise, it needs two reboots. After the first reboot the keyboard / touchpad is still not working and the convertible has to be turned off and on again.
I also attempted the newly released final kernel 4.16. I did even try some daily builds / alpha / beta releases from different distributions (Ubuntu, Fedora), but they all show the same behaviour. I searched a lot of github projects regarding “tablet mode” and “tablet mode switch” etc., but I couldn’t find any specific for my Acer Spin 1.
There is a device which is very similar to the Acer Spin 1 SP111-32N. It is the Acer TravelMate Spin B1 Convertible - this device is as far as I know even shipped with a linux distribution Endless OS. Because the specs of both devices are almost the same, I hoped I could try it on my convertible, but I cannot get Endless OS to boot. Looking in the their support forum, the newer Intel platforms will be supported by Endless OS in the next beta / release.
Overall Manjaro does work pretty well with the Acer Spin 1, almost everything is working out of the box and I hope I can solve the last remaining part with the “tablet mode”.