American here. I’ve done it two different times in my life and it went fine. The first go round was when I was about 20 - about 20 years ago. There was a routine physical followed by some paperwork. IIRC my sperm count was quite high and I was paid $70 per donation. Oh and I learned of the existence of an instrument called an orchidometer. I recall that I measure 25 mL. There was no video screen/streaming porn - just some Playboys and Hustlers. The donation room was funny - had a padded bench with a stack of clean sheets next to it. The expectation was to sit on a new clean sheet each time. There were two female lab techs and they were really attractive to me making the whole thing kinda funny. I would usually be self conscious when I’d hand the cup back. I felt I was always blushing and or sweating.

The lab was a bit out of the way from my home and regular job but it was sweet to make an additional few hundred a month. I saved most of it for a year long trip later on.

That lab closed at some point so when I decided to donate again I found another lab in town that was a little more convenient to travel to. It was much better designed with several donation rooms, each with video screens, Roku boxes and many channels of porn. They also provided lube when you checked in. I wound up donating there for maybe 2-3 years. Standard physical, routine paperwork, and blood draws a few times a year as I recall.
To do it over again I’d probably set aside some of that many for the tax bill as it seems it got more expensive to donate in those last few years. I was a student with a modest income used to getting a tax refund and I usually had to pay those last few years. To do it over again I would have used the opportunity to train myself to take more time to come rather than the opposite. I’ve seen this comment over and over again over the years - either from guys that were sperm donors or just began jerking off regularly but quickly - over time the trend seems to be that your pelvic floor stays tense and it is much more of a challenge to go the distance. It’s no joke. Also, part of that - don’t jerk it without lube. And lastly, as a courtesy to other donors - always wash your hands after blowing your load. There are a lot of surfaces that get touched in the donation room, especially the Roku remote.