@kshegunov Right... Thanks, something didnt trigger in the brain. Now its fine:

connect(uap, &CUaProxy::uaItemChanged, this, [this, i]( const CUaProxy::MsgType msgt, const int riskIndex, const QVariant& value) { this->onUaMsgReceived(msgt, i, riskIndex, value); }, Qt::QueuedConnection);

Also needed Qt::QueuedConnection eventually.

The solution was to set the text browsers setTextInteractionFlags() to (textInteractionFlags() | Qt::LinksAccessibleByMouse).
In my case:

textBrowserReadConversation->setTextInteractionFlags(textBrowserReadConversation->textInteractionFlags() | Qt::LinksAccessibleByMouse | Qt::LinksAccessibleByKeyboard);

I found the solution here:

https://forum.qt.io/topic/70075/qtextbrowser-anchorclicked-not-emitted/2

But I'll leave the topic, because it was hard for me to find it through google or the search engine on this forum.

@SGaist
Good idea, I hadn't considered that approach.
Thanks for the help!

I played around with scrollbar calculation a long time ago and I remember that it was a bit confusing.
But AFAIR you have to set the QScrollBar::setValue() relative to QScrollBar::maximum() with the same ratio as QAbstractScrollArea::widget()::height() / calculatedPos.
(not sure - just guessing...)

Done.

https://forum.qt.io/topic/64346/qtextdocument-and-multithreading

Applied to my code, marked as [SOLVED]. Thank you once again!

You can try taking a look at QTextDocument::drawCursor