Also a recent transplant to the Manchester area (originally from GA), I’ve managed to find a few good places to ride around town. There’s nothing technically in the city, but there are great trails <10 mins away. Some of my favorites are the FOMBA trails off NH-101 (these can be crowded, they’re a real hot spot), the Musquash Conservation Area in Londonderry just south of the airport, and the Horse Hill Nature Preserve in Merrimack (personal favorite; good scenery, trail variety, and well marked). I hear that Bear Brook is the jam, but I haven’t made it up there yet. PM me if you are looking for a riding partner.