Unfortunately OBS does not support MxPEG. OBS supports most codecs out there, including H264 so both codecs provided by the MxCamera in the RTSP stream. M-JPEG will be supported in the P3 platform (x4 and x5 camera models) and both M-JPEG and H264 in the Mx6 series.
This method can be used to stream the camera from a cloud solution using dedicated online servers, there is no need to have a PC online at home as there are many providers with competitive prices. Another option is a technological partner who supplies such services.