I heard about FreeBoB, but it seems like it's an
(very) early project,
and that I shouldn't count on it.
Are there any recording devices like the "Focusrite Saffire", the
"Alesis iO-26", the "RME Fireface 400", the "M-Audio Firewire
410",
etc, that are around 350$USD and that Linux supports?
no.