sftp files to F5 for support

Should still work. Take a look here:

https://my.f5.com/manage/s/article/K000090853

Also note the following:

Secure Files supports the Secure File Transfer Protocol (SFTP) protocol, but only a subset of features provided by many SFTP clients. The SFTP server does not support or allow setting file ownership or permissions, updating timestamps, or creating symlinks.

Hope this helps. I believe the password used to be linked to the support case ID. With the recent introduction of MFA in most instances (interactions with F5 sites) things may have changed. So you may have to call F5 support and check on current procedures. I would also advise support to update the online documentation of things have changed.