This method is pretty bulletproof for me:

As per this page How To Install Speedtest-cli On a FreeBSD To Check Internet Speed, I simply ran these two commands in the GUI at Diagnostics / Command Prompt / Execute Shell Command:

pkg search speedtest

This returned the following:
py38-speedtest-cli-2.1.3
Command line interface for testing internet bandwidth

so I ran this command:

pkg install -y py38-speedtest-cli-2.1.3

Then from there I simply run speedtest