Minecraft 1.20.5 has changed syntax on many commands, so most commands will no longer work without an update.
An update is in progress, you can check compatibility progress here.
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Try the Commands Troubleshooting and Help page if you get stuff with server errors.
New Spawn Eggs in Minecraft 1.20.5 java
Armadillo
Minecraft Versions Permalinks
If you find yourself using a particular version all the time, you can link directly. There is some crossover between versions, so there will be quirks.