For those concerned about entering your network info into an online qr tool, some time ago I attempted a minimal JS and transparent site for generating these codes (https://github.com/jamsinclair/wifiqr).
Or I suppose just use the cli tools, as mentioned, for extra safety...
Arguably it is easier to verify that a webapp is not sending the data to a 3rd party, than it is to verify that the CLI tool doesn't (easy network inspection from the developer tools).
I don't think it is that problematic to put your WiFi credentials to a random website, since the possibility of the creator is a scammer AND lives near enough to you so it can exploits that fact is really small.
However sure, having the piece of mind that this will not happen may still make it more worth it do it yourself.
Or I suppose just use the cli tools, as mentioned, for extra safety...