It is possible to capture screen images from a Teams phone using a web browser page. Please note you do need the phone admin login to use this.
Firstly you need to ensure that the device configuration permits screen capture. To create and assign a device configuration profile, go to the Teams Admin Center and under Devices > IP phone choose Configuration profiles.
The setting you need to switch on is the Screen Capture setting
Once the config has been assigned you need the IP Address of the phone and put it into the link https://PhoneIP/screencapture
But how do you get the IP? Well you can get it from the phone itself. These screenshots are taken from Yealink TP55A.
Tap the profile picture on the home screen
Select Device Settings
Note the Device IP
Open your web browser and navigate to: https://PhoneIP/screencapture, replacing the words PhoneIP with the IP address of the phone. You may need to use the advanced options to continue to the page, depending on your network configuration.
Sign in using the device Admin account. The defaults are different by device and the password is controlled by the device configuration policy. For my phone the username is admin (all lower case)
Once signed in use your preferred screen clipping tool to take screen shots from the web browser
To take my screenshots for this blog, I use an combination of the built in Windows snipping tool, ZoomIt https://docs.microsoft.com/en-us/sysinternals/downloads/zoomit and Snagit https://www.techsmith.com/screen-capture.html