Hobbies are always good, and finding what you enjoy can only be done by trying different ones! Many people with bpd are creative so look into writing it can be a diary, write down anything; your emotions, what you’ve seen, done, or you can try novels or writing poems, join a writing class. There are lots of great ways and you’ll find what you enjoy.
Music, for example maybe join a choir, there might be something local, or try learning to play an instrument. Art is another hobby and many people find it calming and enjoyable. I could be drawing, sculpting, painting, or photography for example. A reading group could be something perhaps? Horse riding has always been a hobby that I enjoy very much. Downside is can be an expensive hobby. Amateur theatre could be another idea to try out.
Be open to try different things and remember you don’t have to be ‘perfect’, learning or improving is very much part of the joy!