baremountain wrote:An analog mixer will only send you L+R out at best
Not entirely accurate, unless you're just wading through new production sub $100 options.
A lot of mixers have a sub-mixing bus that will allow you to mix n channels into four, or eight, or sixteen (etc. look at common multi-track tape machine track counts to see why). Another method is a direct output on the (mixer) channel, so you can fold out the preamp/EQ settings to its own (recorder) channel, while also supporting grafting a few other tracks to a stereo stem, etc.
I highly advocate having a mixer, though it is understandable in this day & age the physical space a mixer occupies makes it undesirable for some. I probably own a dozen mixers, they are wonderful.
Multi track A/D D/A conversion is a must though, I'd start there. You can cheap into an old PCI card system if you run a tower.