Settings
Applications and notification
Show all (number of) apps
"Three dots" (in the top right corner)
Show system apps
Find and deactivate:
Facebook app installer
Facebook app manager
Facebook services
[Edited in 24/05/2020 20:00: Those three are just telemetry apps.]
Yes, those are there even with all of the Facebook apps uninstalled.
Also, I advise you to tweak Device manager and PowerMaster (both are under Settings>Advanced>Device manager).