This is a list of interfaces tested for the series Interfacing Linux. Nothing here is guesswork. You can view the Jack Studio Setup if you’re curious. If you’re tracking down xruns the XRUN Debug page is a good place to start.
USB
Apogee ONE (2009)
Behringer FCA1616
Digidesign Mbox 2 Mini
Douk Audio U2 USB
Focusrite Scarlett Solo (Gen3)
MOTU M4
US-TASCAM 16X08
FIREWIRE
Apogee Duet (2007)
Behringer FCA202
Behringer FCA1616
Digidesign Digi 003R
Focusrite Saffire Pro 40
M-Audio 2626
MOTU 828MKII
MOTU 828 MKIII
MOTU Traveler MKI
Phonic Firefly 202
Presonus Firestudio 26×26
PCI/e
Busted
Digigram VX222v2
Behringer UV1
Linux Audio Interface Benchmarks
While many kinds of audio latency metrics exist, one useful and well-understood metric is round-trip latency; the time it takes for an audio signal to enter the input of a device, get processed, and exit the output.
The following measurements were taken using jack_iodelay.
USB Round-Trip Latency

Firewire Round-Trip Latency (FFADO)

PCIe Round-Trip Latency

Testing setup
CPU | AMD Ryzen 5600G |
RAM | Corsair Vengeance LPX 16GB |
Motherboard | MSI B550-A PRO |
GPU | NA |
SSD | Samsung 840 |
PSU: | EVGA 600 B1 |
Firewire: | StarTech PEX1394B3 |
Network: | Connectx 3 |
OS: | Debian Testing |
Kernel: | 6.0 RT |
Desktop: | XFCE 4.16 |