I have just returned from a trip across several locations in Ireland and London. Masks are still used to some extent but for the most part not very much. My trip ended in London and I scheduled my Covid test for USA reentry with Express Test. They have a testing site at Heathrow and one in Paddington Station. I initially set up my test for the Heathrow site and later showed up at the Paddington site as it was close to my hotel. Unfortunately they would not test me and I had to buy an extra train ticket to go to Heathrow for the test the day before I flew home. Luckily I tested negative.
I was so nervous thinking about the implications of this test that during the pre-test days in London I only visited outdoor sites, I stayed out of the tube or buses, and I only purchased take out meals to eat in my hotel room.
I will not return to Europe until the testing requirement ends.