I have some hue light (ZigBee) for some years and they are rock solid but pricey. That being said, another possibility for your issue could be wifi interference, you could try to analyse and change wifi Channel on your router to see if it gets better.
Mines are not outdoor rated, they are just bulb behind (don’t know the word in English) https://duckduckgo.com/?q=applique+extérieure+lumière+&t=fpas&iax=images&ia=images
Here is one outside rated (but should have more available) https://www.bestbuy.com/site/philips-hue-white-welcome-outdoor-floodlight-black/6326654.p?skuId=6326654
It is normal behaviour to have them locked to 2.4ghz (just like any other wifi smart things). And it is better that way as 2.4ghz has a longer wifi range than 5ghz.