During the night from 15th to 16th of July, I did sneak into the server to do some maintenance while no one was looking!
I did upgrade the world format which should increase performance during play, as the server won't need to do it on-the-fly anymore.
Furthermore, I reset the Nether, but not just a plain reset, no! I generated a new Nether locally with 1.16.1 and then uploaded it to the server so that you may enjoy the new Nether which is totally worth it. Because the server will want to generate it with the original seed, there will be some harsh borders in the Nether for when you go over to the server generated parts but I think it looks charming. If it becomes an issue I can always generate a bigger Nether locally and upload it to the server if needed, but there will always be a border eventually which you can simply work yourself through and explore further, so don't worry!
Go check out the Nether and let me know what you think!