Threema Web doesn't work with Nebulo, even if excluded
Threema Web is not able to setup a connection with the Threema app, even if Threema is in Nebulo's exclusion list.
Threema is an E2E messenger, similar to Signal, Wire, etc. Threema Web (https://web.threema.ch/) is a web app that communicates with the Android Threema app, using WebRTC, I believe.
This problem is not isolated to Nebulo -- the Quad9 Connect app also fail causes Threema Web to fail, but succeeds if Threema is in Quad9's exclusion list.
On the other hand, other split-horizon DNS VPN apps like Intra and 126.96.36.199 have no problem at all allowing Threema Web to communicate with Threema, no exclusion necessary. And a full-on VPN, Windscribe, also works fine with Threema Web.