Great, works fine!
Here a short tut. I’d use adblink on my laptop (Ĺinux.Mint).
- install captiveportalcontroller
- allow ADB über Netzwerk in den Entwickleroptionen
- connect device with adblink (ip:5555)
- in ADB shell type: pm grant io.github.muntashirakon.captiveportalcontroller android.permission.WRITE_SECURE_SETTINGS
- choose custom servers in captiveportalcontroller
- restart wifi
- be happy