Happy to report zero issues in Gdansk, most tourist places will take cards and contactless. If you go off the beaten track you may find you will need some cash, Poland is still a very underbanked country (as you will see by the crazy number of bank branches there are).
Using the Google pay too zero problems, again, just make sure you are paying in Zlotys and not GBP so Monzo can carry out the transaction.
Great town and some great places to visit, highly recommend the World War 2 museum, allow at least 4 hours to get around it. Probably one of the best museasums I have ever visited, not really recommended for children though.
I’ve been there recently and Monzo was accepted almost everywhere. I bought a bottle of (lime) Pepsi costing zl1.50 using my card in a supermarket. There was something else that happened in Poland that I really appreciated - if your card is declined for contactless due to it being the 11th transaction/above the floor limit/above the cumulative limit, you are then invited to input your PIN (without inserting the card into the machine) rather than told your card has been declined and then trying to encourage “disinterested 16 year old shop girl” to try it again with the PIN pad and card inserted.