I'm looking for an online service that can measure the load time of a website, similar to Uptrends or Site24x7. Alert capabilities would be nice, but not needed. The best I've found is GTmetrix, but the frequency of the free plan is at most once per day.
Since a serious attempt at this is relatively expensive (a headless browser must load the target site), I wonder if there's a free service that provides this functionality. Searches on Alternativeto.net have been fruitless - I've looked at all the alternatives to Site24x7.