So this site is about natural insemination I.e. sperm donation through sex (lol):
https://www.coparents.com
The idea is you message a woman/couple (or they message you) about sperm donation and you could have sex with and impregnate them. Or maybe you just donate to their local sperm bank and then they just choose your sperm? I am not sure
Then there is this guy, Ed Houben:
https://www.bbc.co.uk/news/world-europe-26636166
Ed Houben has an unusual pastime. He has slept with scores of women who seek him out for his legendary powers of insemination. As John Laurenson discovers, he doesn't charge.
In a farm house in north-western Germany, heated by a lively fire in a wood-burning stove, a bulky and bespectacled Dutchman - he freely admits he is a bit on the heavy side - makes his way upstairs to the baby's room.
Ed Houben has come to see his daughter for the first time.
He talks gently to the six-week-old baby, and little Madita looks up at him. She is, he says, his 98th child.
Mr Houben is a "charitable sperm donor". He helps lesbian couples, single women and heterosexual couples with fertility problems to have children free of charge.
He started out in 2002 donating sperm to a sperm bank.
But his sperm donating career (he has a day job, by the way, as a tour guide) really hit its stride when the Netherlands, like many other European countries and Canada, banned anonymous sperm donation and he started offering his services for free on the internet.
'Looking for Ed'
He now donates his sperm in the "traditional way". Using the apparatus God gave him rather than a syringe. "Much better chance of conception," he says.
This is his website:
http://www.edhouben.eu/home-en.html
He has had over 100 children. I think he has been so successful because he was one of the first guys to start his own site and service and has developed a good reputation so women go to him despite his below average looks and unremarkable job.