From a networking point of view, I can't see ANY way that you can collaborate in real time like your original post suggested. You will always have lag. I don't know why this topic seems to become advanced calculus. Make your tracks, send them any way you like, let them make their tracks and send them back. This must go on a million times every day given the number of home recorders there are. Dropbox, wetransfer, transfernow... there are so many free FTP options. Send the file, when the other end gets it do a Zoom meeting, let the other side play along on the Zoom call for your approval, then they can record the track and send it back. Network lag is what it is. When you do a Zoom call, you see you in real time. They see you a second or more later.

I am using the new 1040XTRAEZ form this year. It has just 2 lines.

1. How much did you make in 2023?
2. Send it to us.