https://www.max.se/maten/meny/green/
This, imo, is more important than serving the token plant based one, which on the other hand is better than zero. Gotta start somewhere.
edit: actually, all those linked above are non-meat stuff, all 13 of them.
I don't know if it was nationwide, or regional. It came out around the same time as the McDLT, which was awesome.
(As an aside, one of the things that has always bugged me about McDonald's is its menu inconsistency from market to market. The franchisees have too much power, IMO. I have to drive a few hundred miles each year to get McRibs because the local franchise owners won't carry it. And McRibs don't freeze well.)
Although, I do also wonder if a plant is the same thing colloquially as a "plant based alternative".