Is there any record on this specific variant of the character 選?
Apparently the Vietnamese used Chinese characters a long time ago, perhaps only in learned circles. They also created their own "Chinese" characters, which were not known in China.

I had a similar case of a character I could not find. I downloaded some fonts called HAN NOM A.ttf and HAN NOM B.ttf, then I could write the character, but I can't remember what it was now.

Maybe you can get some leads here:

https://en.wikipedia.org/wiki/Ch%E1%BB%AF_N%C3%B4m