PBS SpaceTime has a treatise on relativity. There are a dozen videos worth watching on this topic alone. The video about “the speed of causality” is the one that caused me to level up:

https://youtu.be/msVuCEs8Ydo

Here is a 12 video playlist on relativity:

https://www.youtube.com/playlist?list=PLsPUh22kYmNAmjsHke4pd...

Here is a six video series on measuring space and time:

https://www.youtube.com/playlist?list=PLsPUh22kYmNBkabv9M4fX...