Edent, 
Why is there no formal specification for otpauth URls?
Yes yes, Cunningham's law etc etc!
I want to play around with 2FA codes. So, I started looking for the specification. Turns out, there isn't one. Not really.
IANA has a provisional registration - but no spec.
It links to an archived Google Wiki which, as we'll come on to, isn't sufficient.
There's some doc
https://shkspr.mobi/blog/2022/05/why-is-there-no-formal-specification-for-otpauth-urls/