Any Bluetooth device which presents itself as a serial driver will work with SNIP.
The connection between the device and the PC running SNIP is made like any other serial port. The serial port appears on the serial casters tab along with other devices. Setting up a new connection is found here.
The most common reason to use a Bluetooth connection between an GNSS base station (an NTRIP Server) and SNIP (the NTRIP Caster) is to keep the GNSS device as close to its antenna as possible (reducing the length of the coax run, and hence signal loss). It is not uncommon to place the GNSS device near the roof access and then use a technology like Bluetooth to repeat the data to the PC running SNIP.
However, it is more common to use a Bluetooth connection between a field radio (such as a cellular phone) the Rover GNSS device. And, SNIP works with all of these, but this is more of a rover side issue. The issue is related to whose NTRIP Client software which you elect to use. Here and here are short lists of the most popular clients to consider, many of which are free.
There are many USB to Bluetooth and serial/UART to Bluetooth devices available. Two popular brands which we and others have had good experience with are Brainboxes and SENA Industrial. The SENA product line also includes some network devices which are of value if you are connecting a multiplicity of different GNSS device, or need to connect multiple serial ports from the same device.
USB to Serial cables, converting, physical plugs types, and other connection issues? Check this article.