Where to get Windows 10 License Key?

I need a Windows 10 product key for my new 14th gen build. I'm cautious about buying from cheap resellers because their keys often fail after a few months, especially following a reinstall. I've seen that Microsoft no longer sells Windows 10 keys on their website, only Windows 11 licenses. Are Windows 10 and 11 keys interchangeable, or do I need to find an old, genuine Windows 10 Pro product key?