Ultimate fix: called Delta and got a new cartridge under warranty. At least the video shows disassembly for that.
Fix for creaky delta kitchen faucet by lubricating RP50587 cartridge.
Faucet is a Talbott 16968-SSSD-DST.
Be sure to tighten the large nut holding the cartridge in or it will leak out the bottom of the faucet though the hole in the counter top and down under your sink (don’t ask how I know). Check for leaks.