Maybe 30 years since I last did this, and it seems A LOT harder than I remember.
In those distant days I drove onto the deflated tyre, or I used the foot of a bottle jack next to the rim with the weight of the car on the jack.
Not working for me any more, just slips off, so desperate improvisations are called for.
Ethnic bead breaker
Could have been made for the job. Unfortunately that was a very long time ago, and the wood behind the ploughshare is a bit rotten.
If I had the water buffalo it probably originally came with, I might be able to get that to stand on the bead, but unfortunately old equipment like this is often incomplete.