I have the same issue with the tyres on my MTB - they are WTB Ranger wire-beaded tyres on WTB i25 rims - no way they were coming off with levers and I don't have a vice. I did a similar YouTube search and found a technique that worked for me and may also work in the wild. It involves finding a log, bench, kerb or whatever that is solid with a pronounced edge. Lay the tyre/rim interface on the edge, stand on the tyre, grab the rim and pull upwards like a Bulgarian weightlifter. This got both tyres off and I refitted them easily enough with just levers. However I now have to get them off again and am putting it off because of this effort!
EDIT - I was dreading having a tyre issue in the wild - luckily it never happened until this week, where I was close enough to home to walk the last 200 yards after a deflation that I subsequently discovered would not be fixable without having to remove the tyre.