Anecdotally, it takes far less strength training than one would expect, too, to maintain muscle mass. From what I've experienced, 30 minutes a week, given sufficient stimulus, is enough.

There are more and more PhD researchers focusing on resistance training these days, and yeah, it turns out the minimum effective dose is waaaaaay lower than we previously thought.

https://www.minimumdosetraining.com/ - free training program + links to a bunch of studies the author was involved in on this specific subject.