Take video with multitrack audio on android phone?

Got a multitracker app for my phone, want to shoot video while playing a new track plus previous recorded tracks. Multitrack works OK. Recording with condenser mic from analog mixer. Trrs to 3-rca cable links mixer to phone. Monitor with earbud from mixer. Need to keep mixer levels way down otherwise no prob. Need to get the right video app or can't use external mic (or so they say) but not finding one with multitrack audio. Googled it but nothing.

I could eventually put it together in reaper but that would defeat my purpose - quick and dirty. Making it to send to a peep. Just garage stuff. Possibly it's impossible.

I know "Yes but why would you want to do that" is often the most useful response but I'm already considering that.

Found a couple apps to do that but they're needy. Hate needy apps. I should have said without paying $10 or $20 a month subscription.

They say combination of imovie and bandcamp will do it on iphone but there goes quick and dirty. Also bandcamp is too needy for me. I only like apps that sit in my phone and do what I want without asking questions, making offers, or going online.

F it. Have to use the zoom and a camera app. Multitrack app is ok for messaging audio but it doesn't like the mono in. Another piece of gear to take a mother video but have mixer and effect box already. If only phones have trrrs instead of trrs.