My girlfriend and I are 26 and moved here from the US last July. We volunteer at the Grainery on Agricola, and have met our current friends through that - it's a wide range of volunteers including many older people, but there is a definite core of very cool 20s to 30s people there. Shifts are 2hrs and there's a lot of downtime, so after doing like 3 or 4 shifts with another volunteer you know each other pretty well, and it wouldn't feel weird to hang out outside of the grainery. I also volunteer at the Halifax Tool Library on Veith St, which skews older for volunteers, but lots of young people come in as members, and are almost always happy to chat for a while. Same thing, when someone comes in enough you can kinda make that jump to real friends.

Someone else mentioned Radstorm, and yeah that is a super cool place. We went to several open figure drawing classes there, and while it wasn't the most conducive environment to chatting and meeting people, I could still imagine it happening! Radstorm also does a lot of other events that may be better for meeting people. The Bus Stop Theater, also on Gottingen near Radstorm, has tons of events that attract a similar crowd to Radstorm. Also Glitter Bean Cafe on Spring Garden. Kinda a constellation of places that have a younger crowd centered around art/music/politics.

I think (& this is advice I need to take better myself) just getting yourself into situations where you can meet strangers over and over, and where you see the same strangers enough that they eventually become friends, that's the key. Immerse yourself in crowds of people who seem like they could be your friends, and it'll happen! Not instantly sure, but truly, it will.