Just a quick update...
The Yubico Security Key works just fine on Linux with the "large financial institution's" web site from my Linux machines. On Ubuntu Mate 16.04 (Raspberry Pi 3B+) and 18.04 on an Intel box the process was seamless. On CentOS 7.5 I had to add a udev file as shown on the Yubico site
https://support.yubico.com/support/s...key-with-linux The referenced udev file was NOT present on Ubuntu but it worked anyhow(?)
The only issue I had was when I left the key in the USB slot after logging into the web site. In one case - Google Chrome on CentOS 7.5. - I allowed the site to time me out, closed the browser and powered down the test PC. Later I booted it back up, called up Chrome and found that I WAS STILL LOGGED IN
Might have been something to do with the Chrome settings which I had left as installed.
The other issue, which happens on all machines and on Windoze... If the key is left in and I log out and try to log back on, my credentials are no longer recognized. So as long as I pull the key after a successful logon - I am good to go.
For what it is worth... if I could successfully run the "register" test on Yubico's site
https://demo.yubico.com/u2f then that machine would connect to the financial web site.
Ken