Does serial comm with Uno need level shifting?

The TX and RX pins on the MKR 1010, if I want to link to the same pins on a Uno: Does it need to be level shifted for it to work?

I think the answer is yes disregard

You can get by without level shifting on the TX pin of the MKR 1010, because the ~3.3 V logic level of the MKR 1010 is high enough to be recognized as a HIGH by the Uno. You're correct that you can't subject the MKR 1010's RX pin to the ~5 V logic level of the Uno, so that pin does need level shifting.