It's interesting to hear your experience with Ursi in an apartment! It sounds like you've managed quite well, even with the socialization challenges. My friend had a similar issue with their dog, a real little terror around other dogs, but a sweetheart at home. They tried some classes with a trainer who specialized in reactive dogs and it helped. It's great that you have access to open spaces; maybe with the right training, Ursi could even learn to enjoy a Sprunki-powered walk alongside other dogs eventually!
https://sprunkionline.io/