We are now using Flan for claims protection: https://wiki.blazing-coop.net/flan/user_guides/Getting-Started

I disabled most of the fancy but complicated UI for managing permissions down to a hyper-specific level. Instead, you'll get a few commands to allow access to specific groups I configured.
Short usage tutorial:
  Right click with stick to check if an area is claimed
  To create a claim, right click with a golden shovel and select both corners
  Right click a corner with a golden shovel to expand the area. You then right click again to select the new corner
  You only have a certain number of claim blocks, which grows over time.
  Claims sizes are two dimensional. They go up to the max height but only down 5 blocks from where you used the shovel. Dig down to make the claim move down.
  Use /fulltrust, /trust, /containertrust, or /accesstrust to give varying levels of access to other players
  Use /untrust to remove someone's access and /unclaim to remove a claim

I'll update this later as people get confused, there are nice tutorial videos you can watch though.

Advanced usage tutorial:
  The /flan command contains more advanced functionality. Some functionality is blocked off and not mentioned here
  Use /flan switchMode SUBCLAIM to enable subclaims (denoted in iron instead of gold)
  Use /flan switchMode DEFAULT_3D or SUBCLAIM_3D to go into 3D mode, where you click corners of a cube to create a claim
  To prevent mistakes, claim commands only apply to EITHER parent claims or subclaims according to your mode
  Use /flan info to see details about the claim including who has access. This is very verbose.
  Use /publicfulltrust, /publictrust, /publiccontainertrust, or /publicaccesstrust to grant public access to everyone. Use /publictrustreset to remove it.
  Flan commands guide

The map reset is now complete, server is on 1.21.11 now. We've been playing for a few hours now.

Use https://dynmap.starcatcher.us/ to scope out the map and server builds. South and West of spawn is a lot of snow, but if you make it past that you'll be into more temperate biomes. There's a lot of holes in the map. Happens often on server resets, I'll fix it later.

The server is officially switched to Fabric. It's a bit sad, the server is over a decade old but now the old software is gone. I spent days getting it all setup recently, it was a lot of effort but I hope it pays off. The new server should be faster and more closely match vanilla behavior. I'm hoping the Fabric ecosystem will be just as long-lasting as Spigot was.

Creative is still using Spigot. I will switch it to Paper later (as Spigot is a dying ecosystem). I will consider switching it to Fabric too someday, but that would mess with the years of claim history, and could break some builds.