I just wanted to chime in and say that I was able to get the Excursion to work with Subsurface on Mac OS Ventura (Macbook Pro, Intel processor). I believe I'm using the newest firmware (D01-6C), which I installed today.
For me the main issue was getting the device to show up at all on my computer. Turns out BLE-type bluetooth devices (like the Excurision) will not show up in the native Bluetooth menu and the production version of Subsurface kept either returning a "Device Discovery Error" or not displaying any Bluetooth devices when I tried to "Show all BT devices".
I solved this by downloading the .dmg linked here
Index of /downloads/test (Thanks, TnT). This version of Subsurface behaves like expected when searching for all BT devices (no Device Discovery Error and plenty of BLE devices, including one named "Excursion"). The first time you do this, you will likely need to give Subsurface permission to use Bluetooth.
From there, it was super straightforward. Just downloaded my dives and there they were, in Subsurface. No need to power cycle, delete and re-add the computer, or any extra steps that were previously mentioned by others.
However, I still haven't gotten it to work on iOS. There, I sporadically get the device to show up, but even when I do it says "Info: No new dives downloaded from computer".
Hope this helps someone!