A friend of mine had a knee operation in May three years running and had to wear a cast on the leg till well into September.
One place she visited in those three summers was Taizé France, where most of the toilets were squat toilets. The porceline square with steps a bit higher than the main square.
While there were 'sit' toilets those were always a lot longer to walk, more popular so longer queues and often less clean.
So she worked out to use the squat toilets when standing up.
Take good leg out of shorts and undies, (those can stay on leg with cast if they can be held out of the way.
Stand over the squat toilet with the legs as wide apart as the cubicle allows (so on the outside of the toilet square) and let all run that needs running.
With the cast on the leg she was not able to bend that leg at all. She did aim as good as possible by bending the other knee.
The flush did take care of the poorly landed bits when needed, she said.
As a male you can do at least half standing up just aiming down anyway, so it is 'just' the other half you have to be creative.