I have two installs ASL to BCR220 running on mini-pc’s.
there is no official release that runs on RPI4 - the official one runs on Stretch, not Buster.
there are too many audio gaps and break-ups on the current release of ASL/RPI (IMHO) so I am not using it on RPI but rather a mini-PC.
I made my own cables - it’s pretty straightforward. However, cable that Bridgecom sells seems pretty clear that it connects to “URI USB Audio interface by DMK Engineering”. But even Google cannot figure out what MV-1 is…
The current product sold by DMK is called URIx and has some issues. Do not buy or plan to use the EEPROM feature. DMK uses the same memory area for some configuration info and when Asterisk writes the settings to EEPROM it scrambles the internal memory of the URIx making it appear to have failed. Also, the output level of the -x version is lower than the original too. (There are alternatives to DMK such as the Repeater-Builder RIM and RIM-lite - the second one needs a different cable with a DB9 plug),
NOTE: The BridgeCom aux interface has no CTCSS generation or detection: you have to use the USBradio channel to get that. (HamVOIP has an RPI4-compatible version but it seems they do not support the USBradio channel yet).
Ken