I have no idea what I'm doing but I'm going to use as much details as possible and hope this info is useful to someone.
My method of moving shulkers to the overworld is ignoring end gateways for moving them as they sometimes get lost in the teleportation. So I find an end City at a relatively low X or Z coordinate so I can build a 1000+ block bridge from the end City over the void to the mainland. Then I install rails on the bridge leading to the end portal and go build the farm I plan to take them to in the overworld. Once the farm is constructed and I have a rail from world spawn to the farm, I go trap the shulkers in minecarts and push them down the rail towards the portal. I ride behind them to keep them in render distance all the way to the portal and drop them in. They won't go through till you break the minecart so I use an efficiency 5 shovel to 1hit the corner of the cart. Once through, get them back in a Minecart and send them down the rail to their farm. Getting them in is easy if they can't teleport anywhere but in.
If your base/farm is very far from spawn, use the nether for fast travel. There's tutorials on how that works if you don't know