I have always struggled with mobility and flexibility.
I have great things to say about Kelly Starrett and Mobility WOD / The Ready State. His youtube channel is HUGE.
I'm also a big fan of Gray Cook / FMS. I think they integrate beautifully with Pavel Tsatsouline's materials, but it's also just good healthy stuff for everyone.
I have some back / pelvic tilt issues and Stuart McGill's materials have helped me immensely with that.
I tried some videos from Yoga for BJJ (the "Yoga for Rocks" series) and I found them very well delivered. Yoga is tough for me, but I enjoyed that material more than most.
Lately I'm doing an online video course from Ground Force Method and I'm hoping when all the shutdowns end to go do a course with them - it's a program that looks sorta like ginastic natural or GMB or some other movement program, but it was built on an FMS framework by folks who were BJJ/Krav Maga instructors and wanted a readiness program for their students. I'm really enjoying it because it's naturally BJJ friendly but incorporates FMS thinking and lots of mobility/stability work. It's simple (I mean that as a compliment) and well structured. (Real talk - the videos could have been better produced, but the actual material is great.)