Debug paste link:

https://pastebin.com/ZaJX4qu5

Description and relevant errors:

Players that are offline and been on the server are showing in the tab. Picture of that: https://gyazo.com/5511822b10f4d5667af4c7a5b82dd3d8

That's odd. None of your installed plugins seem to modify the packet, and there isn't anything PL does itself. Maybe it's another plugin that uses another library?

I tried removing protocollib and the offline players did not appear... Would a full plugin list help?

Another thing I am wondering about is the following: with OP I am unable to view offline players like this. What perm is required to make everyone not see the offline players and would it give them perms they should not have?

I have been waiting for a fix for this for like a half year. Please find the issue

I don't know what to tell you. I sincerely doubt this is something on ProtocolLib's end, or it would have come up before. Seems to me like some other plugins aren't getting along somewhere