Btw Sync https://support.mozilla.org/en-US/kb/sync is no longer going to support the old EOL Firefox 78 and earlier at end of March so you will need to use a more current version if you use Sync on the old EOL Firefox 78.15.0esr.

Since you appear to be using macOS 10.13 the most current you can use is Firefox 115 ESR (currently at 115.8.0esr) as the last update 115.15.0esr will be in Sept 2024. Firefox 116.0 and later requires macOS 10.15 at minimum to run.

About Firefox is telling me it will update to ver 102.15.1 esr. Might there be any problems once I do that - addOns not working, in particular? Might it automatically run a lot of addOn updates? Changes that don't incorporate my current settings can be a very time consuming task to track down and figure out how to fix.