After over 30 hours of almost no progress with Microsoft support on this we decided to revert the changes back to dotnet6.
ARGOS is back online again.
Apologies to all our customers.
12 hours later, Microsoft is still not beyond "can you scale the Function App up and down? That should fix it."
Done that multiple times already. Somehow, that actually worked on one App.
The others, the critical ones, still in faulty state.
Apologies to our customers here.