Edit: Never mind - it’s not an OSMC issue. I was able to fix my problem by installing a newer version of snapclient from debian-backports. However, for completeness’ sake I’ll leave the original posting as it was.
/Edit
Installing the latest update has broken my homegrown solution for running snapclient as an external player on my Vero 4K. 
Some details:
snapclient is the client for snapcast multiroom audio. It’s in the Debian repositories, so installing it is straightforward. However, on my OSMC devices (a Vero 4K and a Raspi 3), I’ve disabled starting the systemd service by default. Instead, I’ve got two fake MP3s in my music folder (start.snap.mp3 and stop.snap.mp3) and a definition for an external player in my Kodi home folder. This external player is a shell script that starts or stops the systemd service depending on which of the fake MP3s is passed as an argument.
This still works on my Raspi 3 (right now!) and it used to work like a charm on my Vero4K until the last update. However, after the update, something seems to go wrong between ALSA and snapclient.
When I start snapclient manually, I get this error:
(...)
2022-10-03 12-04-44.557 [Info] (Alsa) Using buffer_time: 80 ms, fragments: 4
2022-10-03 12-04-44.566 [Error] (Alsa) Exception: Can't set buffer time: Invalid argument, code: 0
2022-10-03 12-04-44.566 [Fatal] (Snapclient) Exception: Can't set buffer time: Invalid argument
2022-10-03 12-04-44.566 [Notice] (Snapclient) Snapclient terminated.
Any ideas how to fix this? I admit that OSMC’s audio setup is a bit of a mystery to me.