Where to get Windows 10/11 key? Planning to install Win11 on a new pc build.

I'm aware there is a Shopee option but if I want purchase a legit code where can I find it online? (Of course not from Microsoft directly because they're quite expensive) I'm not sure if the website that the youtubers recommended like Keys.direct, allgoodkeys, etc. are legit so I need some insight.

And to people who have bought the keys from Shopee, how long did it last for you before you have to purchase another key to reactivate it? Many thanks if anyone replies. And if I visit PCImage or EWT Technology, how much do they sell those OEM keys for (I think they're OEMs)?

Thanks a lot for the recommendation, as I've checked it looks pretty legit and the keys seem to be Retail ones mostly, will likely purchase it once my PC build is finished, thanks a lot. ☺️

(if people still have recommendations, please comment I'll also go check those websites out, be it for Microsoft Doc keys or any Windows keys or even Steam keys)

I actually don't mind Shopee ones if it's for some programs but I'm still skeptical if it's activating Windows/Microsoft Docs

This is if I buy the key from Shopee instead,
How about when changing the motherboard/cpu? If I change motherboard in the next few years in the future do I have to purchase the key again if I use the keys from Shopee since I heard the keys are bound to the current motherboard and won't be transferable? (idm if I have to buy it again since it is cheap)

Alright, thanks for answering all my questions as always! Appreciated!