Mixing With Mike

Run by Michael White, an audio engineer with 38 years in the industry. It has courses for every skill level, live weekly classes, and a big library of mixing demos and plugin tutorials. Everything he teaches works in any DAW.

MixMentorship

A 12-week online mixing course with Joe Carrell, a Nashville engineer with 12 Grammy nominations. You get weekly lessons, real multitracks to practice on, and live meetups with Joe. He also offers free multitrack downloads if you want to try his approach first.

Home Recording Made Easy

David Vignola teaches beginners how to record, mix, and master from a home studio, without the technical overload. There's a free beginner mixing course and a YouTube channel full of free tutorials, so it's a good first stop.

Produce Like A Pro

Warren Huart's site for people building their skills at home. The Academy includes multitrack sessions to practice on, mixing courses from working pros, a mastering course, and Feedback Friday, where mixes get reviewed. The blog and YouTube channel are free.