Joining server + realm at same time allows player to get effected by gamemode commands and fly on any server.
We joined the realm then quickly pressed escape then joined either a server or single player world. And our player inventory matched on both realm and server, plus we could fly when put in creative or spectator on the realm allowing flight on the server.
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We're tracking this issue in MC-74984, so this ticket is being resolved and linked as a duplicate.
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