Hi do you guys use external audio mixer in your retro gear corner? One could use multiple soundcards\modules in-out ports you with internal mixers, but 80-90 consumer level PC parts tend to be rather noisy side. So mixing sound outside with modern hardware is preffered.

I'll start with my experience. I have been using now couple of years Maker Hart Just Mixer 5 link. I was looking for compact stereo mixer with sliders. Even back then there were plenty of cool mixers geared towards youtube&twitch bloggers with mono XLR mics support, but very few straight stereo ones with 5 or more channels under 100 EUR . I actually went trough "the cheapest noname aliexpress one" phase and it turned out to be surprise, surprise noisy crap with crackling sliders.

I'm actually quite happy with this one.
I have currently following sources to mix Creative SB32 ISA, Yamaha YMF744 PCI sound cards, Yamaha MU50 and soon to be finished MT32 PI (Rasbperry Pi) based external module.
Since mixer has 2 outputs I'm using 2nd one for nice old school Vacuum fluorescent spectrum analyzer module I got from ebay couple of years ago.

Few things to keep in mind based on my experience:
1) One need to find separate clean 5v 1A power source in order to keep noise down
2) Audio cables should be shielded ones

I'm still open to expand/change my setup. One upgrade path could be adding digital mixing capability.
Would you care to share your experience with your external sound mixing setups?