I have informed myself. There is nothing personally-identifiable in the data Mozilla collects in Firefox: https://support.mozilla.org/en-US/kb/telemetry-clientid

Technical data includes information about your Firefox version and language, device operating system and hardware configuration, memory, basic information about crashes and errors, outcome of automated processes like updates and safebrowsing. When Firefox sends data to us, your IP address is temporarily collected as part of our server logs. IP addresses are deleted every 14 days.