I remember Josh said Korchnoi is 1 of the greatest endgame minds of all time. Probably lots of books. as for online resources, this is what i found on youtube:
Viktor Korchnoi's Endgames
endgame focus: Tal-Korchnoi gm 1 Candidates match 1968
Korchnoi - Karpov | Winning endgame against Karpov is pricesless
Korchnoi (some playlist of various channels)
Wait, I found stuff based on a keyword adjustment: The adjustment is that I look up general chess courses instead of endgame specifically. I just crossed fingers that those courses would have endgame stuff in them. This is what I got:
Winning Chess the Easy Way with Susan Polgar: This doesn't have much, but...
'Essential Basic Endgames'
'Essential Endgames ...
some youtube playlists/channels (that might follow some progression)
'Chess Endgames' by channel Hanging Pawns
Improve your endgame with IM Sagar Shah by channel ChessBase India
'Chess Endgames' by channel Remote Chess Academy
ENDGAMES by channel GothamChess (levy rozman) - has only 3 videos so far but even the pawn endgame video seems to cover stuff ...
My goto resource for working on my endgames is the two DVD volume set which GM Nick Pert produced for Ginger GM. In my opinion it has all the endgame knowledge you need to take you up to at least IM level, possibly even GM, in audiovisual format which many of us find easier to absorb than books.
Here are two YouTube trailers for the series, one from DVD 1 ...