I have greyhounds, which some people consider hard to train (they have a very cat-like “what’s in it for me” mentality) and this is the approach I use. I call it “the name game”. Easy as pie and I’ve taught many greyhounds their new name in about 10 minutes.
Agree with this, too. As mentioned, greyhounds… They have a racing name (that nobody actually calls them by) and a kennel name. Sometimes they’ll be fostered after the racing folks hand them over, and their name is changed. Then their adoptive family changes it again. My new boy went by “lenny” in the kennel, his adoptive family called him “Conejo” and then when I adopted him I instantly changed his name to “loki”. Loki fits him better, btw (the little shit, lol)!
When I was training bird dogs people would leave them with me for a few months sometimes. I seldom liked the name they had as it was not convenient to call out a longer name in the filed. I like 1 syllable names. I would change the name all the time and it never was an issue. When they went home they would change it right back or sometimes keep the nick name during training and working sessions but use the old name around the house. Really is no big deal.
I would imagine that most rescue dogs have had their name changed. I think dogs even become bilingual, and when changing masters, learn to understand the new language.