Not that difficult. The border is open to foreigners and the trains are running just fine from Poland and Romania. Airbnb, Uber, and pretty much all the other services you'd expect are operating. Supermarkets are full of food, restaurants and bars are operating, etc. The only nuisance is there is a curfew at 23:00, so everything shuts down pretty early; none of the usual Kyiv nightlife.

One nuisance re: the border is I don't know how easy it would be to get it for a foreigner on their own. Each time I've visited I was with Ukrainians so the border guards didn't even ask me what I was doing. Maybe that's different if you are alone? I don't know. Also note that theoretically a vax pass or negative test is required. But as far as I can tell that's entirely unenforced and the law is only on the books because the government is too busy dealing with more important issues.

Kyiv continues to get attacked by Russian missiles. Heck, my Airbnb last time was just a few hundred meters from one of the attacks in the past few months. But the chances of you personally getting killed are low. As a rough guess it's probably in the same ballpark as your overall chance of dying from normal mortality.

Of course, this could easily change. And Kyiv is only this safe because lots of Ukrainians on the front lines, and working in anti-air defense, are giving their lives in combat keeping Russia away. But their sacrifices are genuinely making a difference. It certainly wouldn't have been safe to visit a year ago when Russia almost managed to invade Kyiv.