We recently returned from France, specifically Nice. I thought I'd report on our experience in terms of Covid travel.
We were unable to get a boarding pass when we did online checkin, so had to see a checkin agent. That went smoothly. She checked we had our vaccine papers and marked it on our boarding pass. She didn't care about the Declaration.
The plane to CDG was about 80% full. I could see a smattering of empty seats, but of course not in our row of three. We were jammed in with another traveler. CDG was a zoo. We had to go through security again for our flight to Nice, and also see Passport Control. There they only took the most cursory glance at our Declarations, and not at all at the vaccine receipts.
We Canadians require a PCR test to return to Canada. There was a pharmacy doing testing in Vieux Nice. They were a bit surprised we asked for PCR. We had to stress that we really did want PCR, as they kept pushing antigen. We paid 10 euros each for a swab and paperwork at the tent in front of the pharmacy, and then walked about five minutes to the lab. There we submitted our samples and paid 35 euros each. They guaranteed twelve hour turnaround, and they met that guarantee. I don't know if we could have gone straight to the lab rather than pay the pharmacy. It was clear the lab was doing tests on French citizens.
Now that we had our results we had to upload to ArriveCan. DH got his right away, but it gave me some grief. It was one of those things where I just left it for the day, tried again (swearing I did the exact same things), and it worked. We each got a receipt code in the app. Somewhere along the line I'm sure I read they prefer a printout of this receipt code, but we never bothered and it didn't matter.
Again we couldn't get boarding passes in Nice. The checkin agents said this was because of testing requirements at final destination, but they didn't bother checking anything. Another packed flight. At CDG they checked for negative PCR test results.
We landed at Pearson and unfortunately found an angry mob at Passport Control/Customs. It was busier than I ever recall seeing it. Lots of people were struggling with the machines. There was some verbal abuse hurled at staff, which is disgusting. When we finally got to a person, they barely glanced at our ArriveCan receipt code that was on our phones. I have no idea if they spot check further. ArriveCan only asks if you have had a negative test, it doesn't require uploading any proof. It does require uploading of proof of vaccination.
I'd say the amount of time spent getting the tests, and then sorting out ArriveCan to be about 70 minutes over two days.
The extra administration required for traveling is worth it, I'd say, for trips of a week or more. I personally won't bother with any short jaunts abroad (USA), until testing is not required.
Let me know if you have any questions!