I’m vegan and have done 10 Rick tours (and 10 going on 11 Road Scholar tours). On all tours I’ve gotten vegan selections for nearly all meals. I always have back up food in case things don’t work out. Usually the first dinner is the hardest as you’ve not had time to discuss with the guide.
I always put it on my personal tour information which sometimes the guides seem to read and sometimes not. I think also they’ve had the situation where someone says they are vegan until something like creme brulee comes out and they are suddenly OK with dairy.
I had a situation where the first meal only had a selection of lasagna (not in Italy), lol). The guide said there was no other choice. I ordered that and ate the side dish without touching the lasagna. The guide said oh, you really don’t eat cheese? Nope I said. I had food in the room and there was no problem with a vegan choice from then on.
I try to be low key about it but firm. I always talk with the guide after the first meetup and emphasize I can forage on my own if a group meal won’t work. I do ask them to let me know. One guide talked with me (and my vegan brother and his vegan sis-in-law, lol) about a particular pub meal on the Southern England tour as he was not sure they could accommodate. We wound up with huge gorgeous salads and fresh bread so it worked fine but we appreciated the heads up.
The hardest place to me was Ireland. England, Scotland, France, Belgium, Netherlands, Germany, Austria, Switzerland and Italy have been very doable.
What tour are you considering?