I tested it with Wind Waker (Tingle Tuner) and Four Swords Adventures (as a controller with a screen for indoor sections) and it worked for both these games. So that’s a good sign.
My main issue is that it doesn’t connect with the GBA very well. There is a clear gap between the GBA and this adapter when connected, so much so that I was surprised it worked. And it’s a very tight fit, taking it off feels like it could damage the GBA.
In hindsight I wish I paid an extra £5 and bought a second hand official one which I know will fit much better.
But at the end of the day, it works.