I made a case for an ESP32-C3 supermini with an external glue-on antenna. The range increase is amazing, and the result is tiny. Plus, it doubles as a night lamp for my dad (triggered by an array of external sensors). In the image, you can see it plugged into a Trådfri Zigbee router (one port of the USB charger = three uses :-))
Get the STL here: https://www.printables.com/model/1286893-case-for-esp32-c3-supermini-with-external-antenna
Any comments appreciated (but if you're concerned about the polarisation of the antenna, please see the note on Printables first :-)).