Bill from Lubbock, Texas is in Italy right now (see his great report in the Italy forum) and made such an important point in his 'from the ground' overview that it's worth repeating for anyone going ANYWHERE in the near future:
Museums/Sights - Guidebooks such as RS and Lonely Planet aren’t very
reliable with the current Covid rules. That’s not their fault, they
couldn’t possibly keep up with all the changes in rules. Check
everything!! Research is what is going to make a trip possible this
summer. Don’t trust Google or any guidebook for opening days/hours.
You have to look at every website or go by the place if you’re already
there.
This is a good rule of thumb even if NOT traveling during these interesting times - hours, rules, entry fees, reservation requirements etc. can change on a dime! - but is especially important right now, and especially if any of you lucky people are going to be first-timers to Europe. Use your books, by any publisher, for background such as historical information, but don't trust them for visiting details. Same from possibly outdated info that could come up in a random google search. If you are confused about the official websites for that information, give a shout on the forum of the country(s) you'll be traveling to and I'm just sure some nice someones will come along to help.
Oh, and the RS team does note on this site any changes that they know about which have come along after the latest guidebooks have gone to press but a similar caution appears on that page too. Here it is for anyone who hasn't found it yet:
https://www.ricksteves.com/europe/guidebook-updates
Thanks, Bill, for that important and timely reminder!