@Axel-Spoerl small updates:
I tried different Gemini browser, namely Sputnik (written in Swift) - works barely better than my prototype but it does work and I could verify the links - they do work, so the problem is within my code somewhere. there is a Qt5 multi browser named Kristall, written with Qt5 and long not updated at all. Porting it to Qt6 should not be much of a problem (some outdated classes, like QRegExp but not much of it), porting it to macOS is a bit more complex so I'll not attempt unless bored. BUT. They also use QSslSocket so now I'll have a read through their code and see where did I go wrong.More updates once I do the read.