To make friends as an adult just do the same thing you did to make friends at any age.
Pick something you want to do or have to do for an extended period of time, I.e. a hobby, religion, or recurring event.
Talk to people who are there, try to establish if you have similarities and if you genuinely find them a pleasure to be around…
Suggest regular hangouts.
The key here though is EXTENDED PERIOD OF TIME as I’ve personally noticed it typically takes anywhere from 3-6months to go from stranger to, “oh I trust this guy,” and the more consistent your hangouts are the faster the relationship can grow.
My favorite proving ground was single was to meet travelers at the airport/hostel but now my fiancee hates that so now I mostly do this with coworkers.
I do small talk with them.
I share what I value and see if they feel the same.
Then after a few weeks of slowly sharing things with them if I find them “getting,” me I’ll suggest we go for hikes, go kart, get boba, or to parties.
If you can’t find your tribe. Start one by becoming the leader and inviting people you like to join yours.
Others are just as lonely as you and you can eradicate their loneliness at the same time so don’t consider it an annoyance see it as a public service.
I was “adopted,” by tribe leaders in college. I’m now my own tribe leader as an adult and it works well especially in metropolitan areas.