DonSerrot

Are you searching in the new biomes? You won't find any in your old Nether areas, just newly spawned ones. Go way far out to load brand new chunks and dig down to like y15.

While it's a snapshot it won't be updated. That'll be saved for when 1.16 is a full release (months away from now), and when Paper Spigot is updated and plugins are confirmed to be mostly working for it. Just like with 1.15 all servers will be updated at the same time automatically. Any servers online at the time will need to hibernate for the update to finalize if I remember correctly, but any already hibernating will be on the new version the next time they are woken up. Once it is updated you'll just need to go exploring. Loading chunks you've never visited before will have a chance of loading in the new biomes, just like looking for bees in updated 1.14 worlds. If you haven't done much exploring in the Nether it shouldn't take long.

I'm not sure when, but Minehut switched from regular Spigot to Paper Spigot a few months back, and it has 0 tick farming disabled by default. The file where you could normally change that setting is also protected so we can't change it on Minehut. There have been A LOT of requests for it to at least be added to the server settings, but for now you just have to go back to older farm designs.

Until they can update the servers just downgrade your Minecraft versions to 1.15. Go to "Installations" in the launcher and select "New", then set the version to "Release 1.15" and you'll be good to go. Go back to the "Play" tab and click the V arrow next to the play button to select what version you want to launch. With how quickly they got the servers set to accept 1.15 clients before they updated I'm sure it won't be long before they do the same for 1.15.1.

That's because the servers are still on 1.14.4 until PaperSpigot get's updated. All they did today was make it so people could still use the servers with the 1.15 client. You seeing the new items in the creative menu is client side only. I'm guessing the servers default items they don't have info for to stone. I couldn't tell you how long PaperSpigot will take to update. Just gotta be patient and keep an eye on the forums.