Republicanism in the UK is either Irish Republicanism or about overthrowing the monarchy, so yeah in our context it’s left wing. /r/abolishthemonarchy for example is what you’d call a republican subreddit in the UK.

The people are a mixed bag though. There’s a class collaborationist thing going on between socialists and liberals pushing it. I suspect there’s a section of conservatives who lean this way as well but less so than the left and libs.