Another video that clear shows he had a an old western-style holster on his right hip. Plus he’s clearly handling tools with his right hand.
https://www.youtube.com/watch?v=_CN90dAbC5Y
As a postscript to your comment on Finicum’s dominant hand, my Dad learned to shoot rifles and shotguns left handed, until the Army convinced him to change.
We both worked on ranches and had dominant hands, but I did a lot of things left handed.
It’s an astute observation but I’m not sure it’s that material. What seems important is that he had both hands in the air until he began taking gunshot wounds.
He had a 9mms in his left pocket, but as you say he note, he might have been a rightie.