You’ll be there at such a nice time of year! I studied abroad there years ago so don’t have specific galleries or wine bars to suggest, but more broadly, here are some of my favorite off-the-beaten track neighborhoods: Belleville and Buttes-Chaumont, southern part of the 14th by Parc Montsouris, 17th into Neuilly, and just generally following branches of the canal. My favorite thing to do there is just walk 10-20 miles a day in quieter parts of town and just get a croissant/baguette/treat of choice wherever fancy strikes (with an extra plug for going to neighborhoods like Belleville where you can eat from different cuisines). I wonder if this is considered touristy at this point, but go see Angela at the Banh Mi shop by République (I think Rue Turbigo) for the best one I’ve ever had. Ugh have so much fun and you truly can’t go wrong!