These are non-conversation servers (i.e., no one but me should be able to post, and I only post one pinned topic); you just join them to get access to the yinglet emoji (assuming you have Discord Nitro). There are a total of four servers (and I'm including one more) and these are permanent invites.
Yinglet Emoji Bank A: https://discord.gg/n2R66DQA4P
Yinglet Emoji Bank B: https://discord.gg/pE697NRDfJ
Yinglet Emoji Bank C: https://discord.gg/d4sEUEc73D
Yingdings: https://discord.gg/f666bKz3sa
Trans Icon Server: https://discord.gg/nhUdNMeYfY
I am deliberately not tagging this post to avoid unwanted attention, but yinglets should feel free to share it. I want anyone in the community who wants to use these emoji on Discord to be able to do so!
(Remember, the handles of server members are visible. There is an option that claims to turn this off buried in individual users' server settings, but I have no idea if it actually works.)