FileZilla Forums

I'm running mac 10.13.6 and had the same issue as everyone else here with expanding FileZilla_3.66.5_macos-x86.app.tar.bz2
I used the default Archive Expander on the mac without success but as soon as I tried to open it with Stuffit Expander, Voila! It opened no problem.
Been using it for the last few days without any issues, this I think is generally an expander tool issue.

upgraded OS 10.14.6 to 11.7.10, now able to install Filezilla. Still perplexed why Filezilla upgrades stopped working on OS 10.14 ...

Looks like Apple changed how tarballs are created on newer versions of macOS, in a way that their very own older operating systems cannot handle.

I have the same issue, with current (3.66.6) FileZilla and I'm indeed on an old MacOS version --- the most modern an Intel MacMini with Adobe CS6.1 can run. So "update your MacOS" is not an option to my type of user; the other workarounds are.