How to run a standalone browser in a live session?

This is in Ubuntu by USB with no install. On my command line, standalone USB browsers are not displayed as executable and generate a permissions error. Permissions do not change on the command line or file manager with no error feedback, eg., Code:chmod u+x firefox as root leaves Firefox permissions unchanged.

I can't get a standalone to run, & I do not know if this is by design or something I am missing.

I discovered the problem in 16-era Lubuntu which only updates to Firefox 65.