Hi guys, I'm thinking about using the Sony RX10 M4 with the Pro Timer 3 for backpacking, bc I would have to carry much less gear and it's got a fixed lens, so there shouldn't be problems with sensor dust spots - does anybody work with this combination? Since the cam got the Multi-Interface USB input, this should work, or are there known issues? Didn't find anything on the forum ... Thanks!

If that camera has the Sony Multiport, and can be externally released via that port (which normally should be possible) it should work with the LRT PRO Timer. However, I have not tested it and therefore cannot guarantee to 100%.
Maybe you have any cheap intervalometer or remote shutter release that connects to the multiport and that you can try before buying the LRT PRO Timer. If any of those devices can release the camera, the PT will also.