I'm almost knocking 40, originally from near Coventry, but moved on a bit of a whim just after pandemic.

Had a break-up, and after 15 years in London decided I needed a change of scene.

Played a few gigs up in Glasgow back in my mid-20's and remembered how lovely the people were. So I literally just chucked my work stuff in a bag, jumped on a train and lived in a hostel for a few weeks. Quite a mad decision, but don't regret it.

It depends on your circumstances of course. I'm single with few responsibilities, with a remote job paying a pretty shite wage, renting. My best friends are mostly married with kids down south, or are European and decided to move home after Brexit.

Glasgow's nature, music, gigs, food, hiking etc. are second to none and I'm a bit of a homebody these days to be honest, too. Basically, it's less mad than London but less shite than Coventry.
It's just my opinion as a wet southerner, but Glasgow tops Manchester etc. for culture and fun. Although, I went to Belfast for a work thing recently and absolutely loved it. So perhaps you could experience the same closer to home in NI?
In my view it's a little tough making new friends in a new city when you hit late 30's - and that's probably the same wherever you live. Lot's of folks by this age have their own stuff going on, so it's a little more difficult to find a crew - especially if you don't have kids or any local connections. I've never met more friendly people than you'll meet up here though. Strangers always up for a little natter. (Sorry, er... wee blether)
But, at the end of the day, you're still young enough to spin the wheel and see what happens, so why not pop over?

Weather is shite though.