on Nikon is hard to use it (adapter does not allow infinite focus), now on Sony i think you could. most common is m42 mount. Most popular for modifications are 44-2 and 44-4 (bigger the number newer lens). They made a lot of them so you can find one for 20-30$
Helios overall is interesting, but it is manual focus lens. There is 85mm f/1.5 that is also quite popular. in the right conditions you get this swirly bokeh. It looks interesting.
Need to borrow that lens to do some portraits.