I downloaded VSTSynthFont.

VSTSynthFont64.dll installed into bb/Data/lib64. I scanned for new VSTs, which found it but initially I failed to offer a default sound font and it failed to appear in BiaB, and would no longer be found. I opened it again via "scan in a specific directory" and selected the linux path /usr/local/lib/vst/VSTSynthFont/ where it found both the .dll and the default soundfont. I'm unsure whether the vst I see as a plugin is VSTSynthFont or a BiaB shim as it has the BiaB logo, but it does have VSTSynthFont in the top-right corner. I selected Options->Files & Folders->Add Folder and added the Linux /usr/share/sounds/ and its sf? subfolders. I was then able to select soundfonts from there. If found sf2 fonts, not sf3 fonts. I think it should find sfz fonts, but I've just added one and it has yet to find it.

I tried playing around in the mixer with BiaB's own plugins, but those plugins don't seem to work (no issue, I'll more likely use plugins in Reaper or those in my Ui24R. They appear to not match the .dll files above, so I guess they're handled elsewhere. I just thought I'd mention it in case you already know any suitable magic, to try to collect it all together in this thread.

Now I think about it, this should probably all go into the tips and tricks area.

Jazz relative beginner, starting at a much older age than was helpful.
Kawai MP6, Korg M50, Ui24R, Saffire Pro 40.
AVL:MXE Linux; Windows 11; Win8.1: Scarletts
BIAB2022 UltraPAK, Reaper, a bunch of stuff.