Could be that lidarr is setting its own permissions for downloaded stuff (look for something like dmask or fmask in the docker config). You might also need to chmod -R so it hits all sub folders. If you have a file or directory mask option, remember that they’re inverse, so instead of 777, you’d do 000 for rwxrwxrwx.
For what it’s worth, Ikea’s LACK tables make great mini racks