Set player UUID (world owner) in multiplayer

Problem:

I have singeplayer world which I moved to multiplayer server (online-mode=false).

But when I log in, I have different UUID, so all my dogs are not mine anymore and my villager discounts are lost too.

When I log in with online-mode=true, I get my skin and UUID is correct.

Using minecraft 1.16.3.

What I tried:

https://www.reddit.com/r/admincraft/comments/29vugf/converting_an_onlinemode_server_to_an_offlinemode/
(answer from veubeke)

I took files from playerdata, renamed them with player names and for my file with my name I changed the UUID to the correct one (with help of NBTExplorer).
Those files I moved to folder named players.

I also tried to change dogs owner uuid, but it had no affect (through /execute and /data commands).

What I need:

When logging in with online-mode=false – I need for myself to get ‘online’ UUID and for other players, to stay it as it is.