Transferring the UUID from online-mode true to false

Hello, I encountered a problem when transferring the world from online-mode: true to false for Bungeecord. Player inventory as well as ender chests are not carried over. I tried to do it according to the articles, but they are quite old and did not bring any benefit.

https://www.spigotmc.org/wiki/uuid-conversion/
https://www.planetminecraft.com/blog/online-uuids-for-bungeecord/

Maybe someone knows what to do with it? It is very necessary to move at least the inventory.