As an "old" tyre fitter, if you do not have a proper bead breaker for breaking the rim seal,- take the wheel off the vehicle, take the valve out of the valve stem to release all the air - use 3 or 4 wooden wedges and hammer them between the tyre wall seal and rim of the wheel, pushing the tyre wall down with your heel, and working your way around the tyre until the bead seperates from the wheel rim.
It would be worth checking to see if someone has put a tube inside a tubeless tyre, as often when a puncture occurs in a tube inside a tubeless tyre, the air will not come out of a puncture in the tyre tread, but out between the valve stem and valve housing hole on the wheel.
Look at the valve stem base (Where it goes into the wheel) - if the valve stem does not hide the hole through which it sits and you can see the stem going through the hole - you have a tube in there , but if the base of the stem is bulbouse and covers around the hole, it is tubeless. New tubeless valves are cheap enough, and should be easy to get, even as far north as you are.