So, finally, I gave it a try, migrating from 14.1 to 17.1, and did the long hard way of backing up everything manually (without decrypting twrp).
I found out, that with 17.1 Encryption is working, when it is done BEFORE installing Magisk module.
The very first impression was quite nice, especially with the dark theming.
The next impression decreased quickly. The ROM does not at all feel as fast and snappy like 14.1, but rather laggy in responding to inputs. Also, battery life is ridiculous short.
The DO NOT DISTURB tile only works with standard setting, (until deactivation). Trying to tap the other options triggers some other things in layers behind the visible dialog.
Some apps refuse to work at all, e.g. an online chess application. (Which is pity, but minor issue).
In the meantime, when trying to perform a reboot, the ROM gets stuck in the boot animation,. Not a bootloop, but not even animating, just frozen picture.
Thought, that probably the device is just too old for modern android version, so , once erased the initial configuration anyway, I decided to try 15.1, but there the ENcrypion is resulting in a bootloop , even with Magisk not yet installed.
Would really like to switch back to 14.1 inmmediately, which is rock solid stable, but for backuo/restoring reasons, I need to take the indirect route via reinstalling 17.1 again, in order to shift my data to a again 14.1 compatible format.
I am very sorry to say, that 17.1 is not stable at all, against my big hope
Because of this messy way of keeping the data save each time, I wont test/try other ROMs again, until at least, TWRP is able to perform DEcryption. (In all day productive mode, an unencrypted phone is not an option).
Would really like to hear form other users about maybe similiar experiences or any hints. Thx!