This is a server-side mod that will save the names of renamed mob/player heads that are placed down, just like chests or banners do in vanilla (Fixes MC-174496 for pre-1.20.5 versions, and fixes MC-270918 for 1.20.5-1.21.8).

Partially fixed (for player heads only) in vanilla 1.20.5
Fully fixed for all other mob heads in vanilla 1.21.9.
This mod will no longer recieve updates for newer versions