Sorry, I had some pressing issues and got distracted from trying it out more. I’ve only got back to it now. It must be an issue with PulseAudio and my soundcard. With a system & Mycroft update + this fix, it seems to work (at least basic TTS responses, I haven’t tested Spotify or anything more complex yet).
My configuration is RPi4 + ReSpeaker 2 Mics Pi HAT + Raspbian + Mycroft installed from git.