Thanks a lot for the information about jack's use with alsa_in and alsa_out! The multiple card use issue is the main reason I don't work with jack often. Ardour not displaying unless I change my gnome theme to "HighContrast" before opening it is annoying, but I like the command line tool jack_capture as a simple, good alternative anyway. I've long ago decided pulseaudio to be a downgrade from ALSA, but I find it working okay with my modern debian install. Because it's functional now, I already had tested each of these devices through gnome's "Settings"->"Sound" controls. It gives an input device level display to prove that's functional, and a UI to speaker-test for output devices. This all works as expected.
Anyway, I just used alsa_in and alsa_out with jack due to your help, and that is working perfectly too. It's pretty fun to be able to record my from my R-26 as a microphone voice-over for all my other instrument device tests. I did need to post process with audacity later to compress the input levels and remove some accidental loud feedback, but it works amazingly.
My UA-4FX usual sound card was the default as "system" to jack, so I really was converting everything to 48 kHz, but that's fine for this test. This is because I started jack with qjackctl using my previous profile for the UA-4FX. I had to turn the UA-4FX's bottom "INPUT MONITOR" switch to "AUTO" (off) to avoid feedback, since both its input and output is connected in the test.
Then, here are the commands to get them running on jack: alsa_in -j INTEGRA7 -d hw:INTEGRA7 -r 96000 & alsa_out -j INTEGRA7 -d hw:INTEGRA7 -r 96000 & alsa_in -j R26 -d hw:R26AUDIO -r 96000 & alsa_out -j R26 -d hw:R26AUDIO -r 96000 & alsa_in -j VG99 -d hw:VG99 -r 44100 & alsa_out -j VG99 -d hw:VG99 -r 44100 & alsa_in -j D05 -d hw:Boutique -r 96000 & alsa_out -j D05 -d hw:Boutique -r 96000 &
Here's how I had them all circularly connected (using qjackctl): system out->INTEGRA-7 in->INTEGRA-7 out->R-26 in->R-26 out->VG-99 in->VG-99 out->D-05 in->D-05 out->system in. "System in" also had a physical line input connected from the analog output of my Roland SC-8850, and "system out" was connected to my amplifier and speakers from its line output.
I ran a ~15 minute jack_capture recording this way, and verified that all devices are, at once, capable of both capture and playback (duplex). All except the D-05 have to be configured to loop input back to output, each through slightly different conventions, but they were all figured out eventually.
This test has delayed my testing of the UA-25Ex, but I'll get to that next, and this was, very likely, more fun.
Thanks again Geraldo,
Lucas