Use a Nether portal chunk loader
Build a portal in the Overworld and a matching portal in the Nether
Send an entity through the portal on a loop
Use a minecart, boat, or item to keep the portal active
Use a hopper clock or redstone timer to automate the cycle
Keep the loader inside the spawn chunks if possible
Use a player AFK spot near the area you want loaded
Use command blocks if cheats are enabled
Use `/forceload` in Java Edition if commands are allowed
Place the chunk loader in the chunk you want to keep active
Test the setup by leaving the area and checking if farms still run