Q.plum tree no blossoms
I have a mini patio President plum tree inherited when moved in. It has been planted in the ground and is rather large. I think it’s about four years old, but so far has not even had any blossom on it.

Your tree may not be quite old enough to bear fruit just yet - it can take up to 6 years. Does your tree get enough sun? Are there any signs of disease or insect infestations?
Here is an article that explains why plum trees do not fruit:
https://www.gardeningknowhow.com/edible/fruits/plum/plum-trees-not-fruiting.htm
Happy gardening!