Minecraft Fabric 1.20.1
Also requires the Fabric-API.
On interacting with a crop plant that is fully mature, the plant will be destroyed and if a seed for that plant is available in the hotbar, it will be selected and planted.
Also supports nether warts.
Because apparently all the others I found (even though they have more features and are better), need a server mod.
This mod runs on the client fully. It does not need a server mod.
Currently, this mod will interact with the farm block, without looking at it.
A vanilla server and Spigot do not seem to mind this.
But if the server has an anti-cheat protection, this mod will not try to hide the automation.
You have been warned, this mod can get you banned for faked packet sending!