Great, that is exactly what I needed. Thank you so much.iperf is pretty commonly used. You would put an iperf server on a pc on your lan (ideally wired into your central switch or router) and the iperf client (it is the same program as the server, just with different parameters) on the machines you want to test.
https://iperf.fr/iperf-download.php
I think there is also a version for android on the play store.