I've found two that work but one is playing up, just append your key where there is [KEY] and save the shortcut
https://totp.danhersam.com/?key=KEY
https://2fa.zone/2fa/KEY (broken but https://2fa.zone/ works)
Example: https://totp.danhersam.com/?key=7J64V3P3E77J3LKNUGSZ5QANTLRLTKVL
And that's why I use a url on my desktop to a 2fa generator that also decodes it with the 2fa key as an argument. It's like a password sticky note on the monitor, but for 2fa haha.
The Pilot G2 and the Parker Quink Gels are great for refillable pens too! Dry ink is always an annoyance
Most certainly not! Haha, you'd need a lot more information than just the key like what the 2fa is for, a username and password. But if your internet access is ever spoofed by someone or there is a hacker that traces your IP address back and tracks your activity, that information can be found.
It should only ever be used for non important things.