I am also on eu-rom, also works great.
I made following steps (different as Kees):
- China Stable - then unlocked bootloader
- Booting China Stable with unlocked bootloader (automatically boots after bootloader is unlocked)
- Reboot into Fastboot
- Flashed TWRP with ADB command fastboot flash recovery xxxx.img
- Then ADB command fastboot format userdata
- Boot into TWRP
- Copied EU rom from PC, copied Magisk 16.4 from PC
- Installed EU Rom and Magisk 16.4
- Reboot into System
Works fine immediately, Magisk 17.3 did not work, so I used Magisk 16.4. It was updated to Magisk 18 in the meantime