Does any wifi adapter exist that does not need closed source firmware?
 

I'm sick and tired of constantly having to buy new wifi adapters
only to conclude that for whatever reason it's firmware refuses to work on my Arch Linux computer.

I've been looking for wifi adapters with open source drivers, but I don't think any exists, or am not seeing this correctly?

Why is this?

I'm not a Debian user, but have a read of this - looks to be a pretty good synopsis.

I bought a TP-Link dongle a while back because it had good range and was "Linux supported". Rubbish - they produced a driver (with source) back in the dark ages but have never updated it as the kernel evolved. Fortunately the community on github have picked up the reins; you just have to find some-one with an interest in your chipset. Recently there have been a lot of changes - since say 4.11.

For Laptops I insist on Intel wifi - at least they talk to the kernel devs and have a blob that Linus is prepared to accept. Much nicer solution.