probably the best idea (or if you have Priority Pass membership, use that lounge).

I highly doubt you’ll be allowed to access domestic side, and even if you can, probably not near worth it. YYC uses pre-clearance, so even if you knew you could go to domestic and get in, you’d still need to leave, go back to transborder area, do pre-clearance and security and get to the gate. This is all a lot of time you’ll need to get to the airport earlier for, to get to a lounge, which, to be fair, I’ve never been to MLL in YYC, is probably decent but nothing special (have visited several MLLs over the years - better than the UC for sure, but visited many other better lounges).

even for someone who sometimes arrives a bit earlier than I need to so I can spend time in a lounge in the same or airside-access nearby terminal, would not ever do this.
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