Sometimes, during measurement, the network speed does not change and the displayed value remains the same, making it difficult to tell if the measurement is still running or has stopped.
Even a simple solution such as adding an indicator with a fade animation displaying "Measuring..." or "In progress..." would be helpful.
Also, this is just a suggestion, but an animation of spinning Doggo could be a cute option.
cf. The running rabbit animation displayed in the top left corner of Cloudflare Speed Test.
cf. An animation of spinning Doggo, on Kagi Search landing page.