Rescue dog needs friends.

I agree that Nextdoor.com is a very useful community website, just for your local area, and I’m sure if you join and ask if any dog owners would like to meet for walks, you’ll get lots of response. Failing that, a word with the local pet shop might help. You could even offer to look after another dog occasionally. Good luck.

There’s a web site called “Next door” or something like that. If you can find it, there could be fellow dogs walkers on there, or you could advertise on it yourself for companions.
Likewise, my village & other villages nearby have their own community Facebook pages. There’s often similar adverts on there such as yours.
Facebook is not the Devil Incarnate & you don’t even have to use your own name if you want to be discrete. Might be worth a try.
Good luck.

I'm far from you and don't even have a dog but I would join you if I could. I hope some other Gran can meet up with you though.