Ask HN: Moving abroad at 30, no friends/girlfriend, need advice

I will move to London to work for one of the big techs, but I know no one there. Most employees work remotely. I have a few friends home but in the long term no one will follow me in London. I have been exploring options to make a few new strong and long lasting friendships and finding a girlfriend there.

Periodically I read on HN stories about how difficult it is to make friends after 30. How shared context and repeated interactions are important, proximity, situations that allow confiding in each other, etc, although in practice I can only think of university as a great option that checks all the boxes, both for finding high quality friends and girlfriends, but that's not an option anymore.

A few other options I considered: participating in activities around the city (e.g. going to the gym, start a sport, dance, go to meetups, join clubs, etc), although I am not sure which things/activities/contexts really work and are attended by smart, social men and women open to expand their social circles. I can think of a few things that might work for some things, but not for others (e.g. go to the office to meet smart people with similar interests, but good luck finding a girlfriend there, considering the gender ratios, or joining a dance class to meet women, but good luck finding techies there).

So, in short, what would be in your opinion the best things someone could do to make strong, long lasting friends and find a girlfriend? I am looking for the most effective solutions, I am open to try new things. My strongest interests are tech, investing, startups, playing guitar, acting, and psychology.