Ok so I have adapted this to open Windows Terminal instead (which is a huge improvement in general over previous options or CLI on Windows...). They key is to use the -d switch to specify the folder to open to.
(Note, this is opening Ubuntu for me, which I have set to be the default in the Windows Terminal settings).
I have the general context menu working fine with:
C:\Users\YOU\AppData\Local\Microsoft\WindowsApps\wt.exe -d {sourcepath}
However, I can't quite get the right click on folders to work - have tried the above, and
C:\Users\YOU\AppData\Local\Microsoft\WindowsApps\wt.exe -d {file}
Though it seems this should probably be added in a more offical way to the CLI options in Opus itself (https://www.gpsoft.com.au/help/opus12/index.html#!Documents/CLI_Command.htm)
Leo - any tips on getting that folder right click to work?