I'll chime in to provide the flying across EU borders perspective. TL;DR: it's a pain in the ass and sometimes depending on how long the trip is, the juice is not worth the squeeze. You can also tell me "QQ/STFU like_that, because you get to travel Europe for cheap."
I don't understand what the purpose of the EU is anymore other than trying to keep the Euro relatively strong. None of these countries are in sync and they change their COVID policies anytime they take a piss. For instance, Italy's policy (like most countries) was you can enter without a COVID test as long as you are vaccinated. Exactly one day prior to flying to Paris, the Italian Government decided they didn't care about vaccines anymore and now require a negative test if you are entering from ANY EU country. We were just going to Paris for a weekend, so we had to scramble to find a pharmacy for testing, which is a lot harder than you think if you need to get that test on a Sunday. Most of Europe shuts down on Sundays. Luckily, our airbnb was right next to a pharmacy that did tests on Sunday mornings. Logistically and for planning purposes it's a real pain in the ass. I can't remember the last time we have booked a trip longer than 10 days in advance, because these countries change their regulations so suddenly. Also, the amount of documentation you have to carry with you when you travel now is obnoxious (passport, covid pass, negative tests, etc). The best part is you're still crammed in these 100% capacity flights sitting next to strangers (most airlines have 3 seater rows). It's all a dog and pony show.
The best part is, once we arrive to Italy they never check any of these things. I returned to Italy from Sudan (don't ask why, but fuck that place) last year when vaccines were not available. It took me about 5 minutes to get thru passport control. They didn't check shit. All I had to do was fill a declaration form that said I was not feeling feverish and I do not have COVID.
I won't confirm/deny now that we have several negative tests from several countries, it is possible to PDF and change the date since they don't scrutinize the tests. We might or might not have taken advantage of adobe...
Don't get me wrong, we are still traveling and living our lives. The fact that we don't have kids helps a lot. I can't imagine doing this with kids.
Edit: The added layer of getting stuck in another country sucks too. It would be better to test positive in Italy, because the worst case is we can rent a car and get back home. If you're stuck in another country, that shit can get expensive, especially if you're just sitting in a small ass hotel room.