Google Chrome and Firefox report the Apple M1 GPU if found. Other browsers just report: Apple GPU (same as on MacIntel based machines)
If the M1 GPU is detected in Google Chrome or Firefox it will turn red. Otherwise it will report in red that this is not Chrome or Firefox detecting an M1 GPU.

Apple M1 Mac GPU Detected on Chrome or Firefox Browser
Not Apple M1 or Not Chrome or Firefox Browser

GPU Detection Source:

Class injection test by Jeff Clayton

Test Site 1:
Test Site 2: