To disable it in about:config
browser.search.serpEventTelemetry.enabled = false
browser.search.serpEventTelemetryCategorization.enabled = false
People really need to kill that notion that telemetry is automatically bad. If the information they are collecting is minimal, as non-identifiable as possible and actually being used to help develop the browser, it’s a good thing.
Yes, turbo nerds in the back, specially being opt-out, opt-in telemetry is pretty much useless for trying to understand the majority of your user base.
Syncthing is one of the best examples of telemetry done well. On first startup, they ask if you agree to enable telemetry, they show the data that will be send and inform users that the collected data can be viewed at https://data.syncthing.net/