Tidal not playing through Squeezebox with LMS in Docker

Starting to rebuild my whole-house audio playback system based on LMS as Roon, while nice, is not as free as LMS. Plus, I can get my LMS to access and play not only local files and Tidal, but also Spotify, which is missing from Roon.

Anyway, in getting back into this, I came across a frustrating issue - I could not get Tidal to play on any client device.

There's a few posts out there on things to check, like Tidal plugin setup in mysqueezebox.com, use FLAC file format etc., but nothing worked for me.

I had a look in the LMS server log file and came across a bunch of these errors;

fh=Slim::Networking::Async::Socket::HTTPS=GLOB(0x563293263068)
[23-03-07 11:43:22.4710] Slim::Networking::IO::Select::__ANON__ (130) Error: Select task failed calling Slim::Networking::Async::HTTP::_http_read_body: Error in tempfile() using /config/cache/tmp/XXXXXXXXXX: Parent directory (/config/cache/tmp/) is not writable at /lms/Slim/Formats/FLAC.pm line 950.

I run my LMS as a docker in unRaid. When I checked my mapped paths in the docker, I see 'config' maps to my appdata/LogitechMediaServer/. Inside there, I used chmod via SSH to set permissions on the /cache/tmp/ directory and instantly the Tidal stream started right up.