Minimalistic BetterDiscord theme; hides Nitro (almost) everywhere, and it's done! But in the emoji selector, the linked plugin should work. (Or more likely messed up the whole thing, but still not late to fix some code...)
HideDisabledEmojis, the DownGit downloader - https://downgit.github.io/#/home?url=https://github.com/rauenzi/BetterDiscordAddons/tree/master/Plugins/HideDisabledEmojis