As of today, 28 Mar 2021, Facebook Container 2.1.2 is BROKEN for 78.9.0 ESR 64 bit. It worked in 78.8 ESR 32 bit, but locked me out after the upgrade. When I turn the extension off, Facebook reappears. Remove, restart, and reinstall doesn't help.
[edit] This version WORKS PROPERLY on 78.8.0 ESR 64 bit. I checked it on other versions running on my network, sync'd to the updated 78.9.0 ESR 64 bit.