OK, thank you!

Can this new setting take on the exchange for the underlying by default?

Another thing is with Primary exchange for stocks/etfs. It is now set to ISLAND (=Nasdaq) by default, but most key ETFs actually need ARCA in this field.

IB allows to specify a Primary exchange via a semicolon (or other symbol), so, e.g. for SPY this would be SMART:ARCA.

But the more robust way is to reqContractDetails() before further reqMarkData or reqHistoricalData calls.