This list will only grow with time. Thought it would be great to have a quick link to go to instead of having to scroll through Google while on the call.
Just copy and paste into your web browser.
Avaya:
Avaya 9608/9608G/9611G IP: https://downloads.avaya.com/css/P8/documents/100176054
Mitel :
Mitel 5330: https://www.nmc.edu/departments/help-desk/telephone-operations/manuals/5330IPPhoneCustomUserGuide.pdf
Polycom: