One thing you could try, if you haven't, is dating someone you connect with, and have a fun time with, even without "romantic spark". Attraction can be important in a relationship, but in a long term relationship spark often doesn't last anyway, and it's other things that actually keep people together. Getting along well, working well together, handling stress in complementary ways, etc, are all more valuable long term.
So just as an experiment you could try dating someone for something "long", but not actually that long in the grand scheme of things. Maybe 3 months, roughly one season. Even if you're not physically attracted to them, try dating them anyway. If it doesn't work, you haven't actually lost anything. Just a bit of time. And you will have officially "had a girlfriend", and gained some amount of relationship experience, even if it wasn't the best.
And if it just so happens that you're just not an "early term" guy, buf you're actually a pretty good "mid-term" guy, then that's great! Keep going! You haven't got a lot to lose, in a sense, so you're available for experimentation.
Can't tell if trolling, quipping, or honestly asking...
I feel like some people who don't want friends are often people with low self esteem who have decided their hypothetical future friends will abandon them, or not like them, or whatever, and so they convince themselves that they "don't want that anyway" as a way of protecting themselves from future pain or embarrassment. In those cases, dating aside, the person should work on their self esteem.
If it's not that, one could try casual hookup apps. These rely on a certain amount of work, and there's no guarantee, especially if one lives in a less populated area, but it's possible.
And the third option for someone who doesn't want anything social and just wants sex, is sex work. This is exactly what it can be for! The only trouble is that in most places it's illegal, which pushes it underground, making it both difficult to find and potentially dangerous... but this is the niche it's meant to occupy.
But honestly... at least consider that it may be the first case, and see if you can search your feelings to figure out "why".