gnirehtet will not properly reinstall on my Oneplus 7 with Android 11

[EisigesEis]

Today, after many years of usage, gnirehtet has stopped working on my device (Oneplus 7 GM1903 with the newest OxygenOS):

For using online banking I had to install the app "SecureGo" (as suggested by my bank GLS). I used reverse tethering for installing the app and kept it running. After opening the app, it opened a webpage suggesting my device has a Jailbreak or Root (https://www.vr-banking-app.de/service/securegohinweis.html - in German). Could this be caused by gnirehtet? I have not rooted my device.

After uninstalling the app and restarting gnirehtet the reverse tethering stopped working. In cmd gnirehtet gave the output "Client #0 connected" and after a while "Client #1 connected" even though there was only the OP 7 connected to my pc. No connections to the internet if I try opening a webpage on my smartphone.

I then decided to uninstall gnirehtet which was probably the worst decision of them all. I was not able to reinstall the app in a proper way with a VPN showing up. The app now crashes on my smartphone upon starting gnirehtet on my pc.

I have no idea if this was caused by SecureGo or simply by the newest OxygenOS version nor do I know how to fix this issue.