Just wanted to add one more:
I found a TYWE3S module in a Tuya plug and replaced the PCB antenna with an external one. The approach is basically the same as in @tom_l’s original post, but the PCB antenna is mirrored on the TYWE3S.
I don’t have a before-after comparison. In my case the plug is used behind the pool where there is absolutely no Wifi signal, but with the above modification I could install an external antenna about 1 metre above the pool water level and ESPHome now reports around -72 dB signal strength.