I have done this in the past..
I tried cutting with a grinder.. lots of smoke and mess.. i gave up..
also tried using some crowbars as tyre levers.. they worked.. eventually..!! but it took a long time and a lot of energy..
a bit of a breakthrough moment came when i used plenty of grease
on the tyre bead and the edge of the rim.. it made levering it over a LOT easier as the bead had a tendency to REALLY grip the rim when it was nice and tight..
breaking the bead was relatively easy.. deflated the tyre then stood on it..
would i do it again? nope not a chance!!! I’d take it to a tyre place and pay the fitter to take them off..