I work on a code base that uses microfrontends so having just a page load primitive is not always enough to narrow down issues with one of the microfrontends on the page.
Some traces I am thinking of self instrumenting myself but would love to see it get discussed more in this group:
mount [microfrontend name] spans for mounting of a microfrontend, different than a typical loading javascript span, each microfrontend has different bootstrapping logic.
microfrontend.id span attributes associated with all frontend spans so you know which frontend is making API calls or running logic