Backup the world and remove gtceu
Loading the map without it will remove all the content of gtceu
Then add the mod again and rebuilt the gtceu stuff - and avoid using the reactor
Make sure you are using Java 8
And start the server via start script (run.bat file)
For example:
"C:\Program Files\Java\jre1.8.0_311\bin\javaw.exe" -Xmx4G -Xms2048M -jar server.jar
pause
Looks like garnished-botany-pots-forge is not a 1.20.1 build
Try this one:
https://www.curseforge.com/minecraft/mc-mods/garnished-botany-pots/files/5467686
If this isn't work either, remove it