Wall panel (android) running on grandstream desk phone - click to call uri?

I have home assistant running using wall panel android app on my GXV3370. I am simply attempting to call a phone number when clicking a button. The button is configured as a URL in lovelace. Aka click a link (on desk phone) to initiate call on desk phone (same device).

I have tried the http tel link tel:123 , not working. I get an error about uri scheme. This is an android thing, not sure how to make it work on this phone. Maybe because i’m doing this from within an android app, not the native web browser?

Perhaps this could work using an intent scheme url?

For example, to launch the Ring app, you would use this as the url schema:

more examples

This seems like an android thing but not sure if it’s implemented / how to use to create call on grandstream phone.

Things I have already researched (grandstream specific):
This is NOT click to call (click phone number in computer web browser to start call on desk phone)
This is NOT action urls (send action to sip server when phone performs some action)
This is NOT to do with grandstreams’s softphone that runs on android devices. (wave)
This is click link url on the desk phone its self to start a call.

Screenshot of home assistant click to call button example:

Posted same question at: