Is it impolite to ask if i can finger my alpha’s hole while sucking him off?
First of all, I commend you for thinking about asking permission before doing that!
I am not sure. I think you should ask him if he would be interested in that first. It’s not impolite to ask. After all, you are seeking ways to increase his pleasure.
Just be respectful, and if he says “no,” you go with it.