Umm.. probably I’d suggest through volunteering.

Local fire service/ emergency service/scouts.

Or local tech communities or social impact non profit.

Get into a space where people are gathering and acting in altruistic ways.. you’ll generally find generosity/community and friendship.

If I’ve been friendly and supportive and unexpectedly stayed till the end and properly helped pack up, support the organisers.. I’ve often had an invite “we’re heading for drinks now/ a late meal, would u like to join us.. [then at drinks].. hey tells us about yourself.. we’d love to have you get more involved..”. Not always but it happens enough that I know I can reliably make friends in a new community by legitimately being of service and I suppose modelling “being a good friend” from the outset.

Intense experiences together can bond deep friendships.. (studying together, helping a cause where you stay up half the night, pushing towards a challenge like in a socially oriented Hackathon/challenge).

Or join a group that meets regularly.. go consistently.. meet and thank the organisers at the end of the night, help stack chairs, hang around till wrap up, get involved.. friendships build amongst the small cadre of folk who make stuff happen and hold spaces for others, even when the main event ends up being more transactional.

Volunteering on a conference is often an easy option.. just reach out to any conference and say you’d like to volunteer.

Just a few suggestions, I haven’t boiled these down into principals but hopefully that gives you a few ideas.

you could have just said friends. Anyway best way is through hobbies and common interests. If you have some interests which could be shared with people then find online groups first and gradually see if they have real life events. Don't mistake your work colleagues for friends, the moment you leave your job you never see them again.