Sorry guys, is been a long time but I finally got the chance to continue the project. This is not an example of how to follow deadlines. Anyhow, it seems that NetHTTP is now fully operational and maintaining long polling requests without issues. As from my investigation the last year, I had several problems to perform this and even the "Cancel Request" method wasn't behaving as should. I'm not sure if Embarcadero did changes to the NetHTTP this last version but it seems very stable now. I was able to maintain more than 20hs of long poll connection without timeout or hang. When I saw that working for the first time it was like melody to my ears and I could finally perform the tests I needed to Android. I prepared an example under samples folder containing the boilerplate to make foreground services run in Android. I didn't have any issues in my tests. The issue concerning reconnection has also been addressed in this version. It was "a hack" but killed the bug with one shot.
Long story short, I'm happy to merge the PR with main and delete this branch once for all.
[EDIT]
After reading the release notes for Delphi 12.1, I was able to understand why NetHTTP is now much more stable. Embarcadero indeed made changes to NetHTTP, but these changes were aimed at AI REST API servers that return data in logical blocks. This ended up positively impacting our library as well, since the ntfy long polling request runs under a similar scenario.
