samem said

I don't have another device that I am willing to sync to.

You don't have to sync any device - who or what gave you that idea  ?

Help! Can I still use Firefox?

Absolutely  !

The installation process states that, for security reasons, I MUST sync with another device. I did not do that. I keep getting reminders that, to complete the process, I am to sync with another device!

samem said

The installation process states that, for security reasons, I MUST sync with another device. I did not do that. I keep getting reminders that, to complete the process, I am to sync with another device!

May I ask what installation process  ?

You don't need to have a sync account to use Firefox .....

Happy112 asks what installation process.

For me it happened after a Firefox update two days ago which looked as if everything must now be Sync'd, so I'm in the same position as samem.

Thanks. I am relieved. Sandy