I do a ton of international travel for work and run everywhere I go. Mostly training but have done ultras and marathons while on the road as well.
All the anti jet lag fad stuff (like starving yourself) doesn’t work. Going to Europe the best thing is to stay up and watch movies on the flight and then stay up as long as you can when you get there. Then your first night you’ll sleep like a log. Then get up in the morning and do an easy run for a few miles. Your body will react to the morning sun and you’ll be more-or-less adjusted. Same thing on the second day and night, but it’ll be a little harder to sleep, but do that same short running in the morning. The 3rd day you’ll be ready to do the marathon.
You can do the marathon sooner, but your legs may not be under you yet so ya might not get that PR.