Algorithm for determining whether 2 entities of some feature are the same?
I am not able to clearly understand your use case, but from what I infer I believe if you are trying to de-dupe data on other features, the approach would be to use LSH(Locality Sensitive Hashing) you can see the following links to get an overview. hope this helps.

https://stackoverflow.com/questions/12952729/how-to-understand-locality-sensitive-hashing

https://www.cs.utah.edu/~jeffp/teaching/cs5955/L6-LSH.pdf

https://en.wikipedia.org/wiki/Locality-sensitive_hashing