I often exercise with friends via videocall, where we all follow along with the same online video. Recently a friend asked for recommendations of free YouTube videos for beginners. Here's what I said:

This New York Times workout is where I started. It's a six-minute workout in total, including 3 different exercise videos.

I really like 2 instructors, who both have YouTube playlists to make it easy to find what you want:

1. Joe Wicks, "The Body Coach." British guy, concentrates on strength and cardio. Here is a 10-minute workout you can do while sitting in a chair. Very beginner-friendly, meant for senior citizens -- sometimes my friends and I have done this one.
2. Jessica Valant. American woman, concentrates on Pilates, is also a physical therapist. She usually talks about how to modify moves to make them easier or harder, based on what you can handle. Here's a 12-minute video that focuses on muscle strength, circulation, breathing, and pelvic floor health.

Wicks and Valant don't have music in the background. If you want music, Popsugar has good videos that also demonstrate modifications you can do for easier vs harder. I think I remember liking this one, "beginner low-impact cardio" (15 min).

(I forgot to mention Hybrid Calisthenics videos to my friend, but I think they're good too. Relevant MetaFilter discussion.)