Watch your Language | Super challenging Proto-Indo-European concepts explained: S in parentheses and Hs with numbers @watchyourlanguage3870 | Uploaded February 2023 | Updated October 2024, 3 hours ago.
Links:
Predicting Future American: youtu.be/F2Jw2ILRBVk
Indo-European sound laws (Wikipedia): en.wikipedia.org/wiki/Indo-European_sound_laws
This video’s sequel about Ablaut: youtu.be/vw-Ow0DJEI4?si=FqHNj8GX_aFYTxv7

Translations:
1:53: (Dutch) where n
2:11: (Probably terrible PIE) When two words end and start with the same sound: “WHERE DOES [s] GO?!”