Microphone > XLR Cable > Zoom P8 Mixer > Dual TRS Male to TRS Male > Canon Lumix.
The camera at the end of that, is your problem, even before you swapped. Don't combine audio and video until the VERY last moment. That would be OBS itself, not before. So run your audio directly into the PC, without the camera at all.
Ideally, you'd use the USB connection on the mixer itself to do that - point OBS directly to the mixer as a "USB sound card" - but if you MUST use an analog out, then you want a USB line input. Here's one that I'd consider to be the cheapest acceptable:
That's a for-real stereo line input. A lot of "audio inputs" are actually mono mics. That's different. There's also a similar-looking version of this one, that's actually a phonograph input with the RIAA correction EQ built-in. You don't want that either. This link here, is good.
Depending on what market your mixer is actually designed for, you might need to keep the volume somewhat low. There's about 11dB difference between pro line level and consumer line level, with the pro version being higher. The one in that link is consumer. Works just fine; but just know what you're using and use it accordingly.