Worth noting that 3Blue1Brown also did a series on linear algebra which is eye-opening to say the least. Playlist at:
https://www.youtube.com/playlist?list=PLZHQObOWTQDPD3MizzM2x...
Even if you think you grok matrices, have a go at the first few videos of that playlist, if just for the visualization. It really helped me see what matrices (and operations on matrices) represent!