SOLVED.
TL;DR: RaspPi 4B has two micro-HDMI, only the one closest to power plug does sound by default (HDMI 0). Both can show display, but only one has sound. I had to move my cable and reboot.
Things I tried that were likely unnecessary:
sudo apt update && sudo apt dist-upgrade
sudo apt remove kodi kodi-bin kodi-data kodi-repository-kodi
sudo apt install kodi
sudo apt autoremove
sudo rpi-eeprom-update
sudo reboot
sudo rpi-eeprom-update -a
sudo reboot
sudo rpi-eeprom-update
Currently have player set to sysdefault - bcm2834 HDMI 1 and Audio Output at default – I had set it to „force HDMI“ but it seems to have reverted on boot. sysdefault counts from 1, its „HDMI 1“ is HDMI 0 and its „HDMI 2“ is HDMI 1.
Debug for good measure, in case others run into this. Choosing the right port should be sufficient though. D’oh.
#### SQUEEZELITE VERSION ####
Squeezelite Max2Play v1.0.3 based on v1.8.7-999, Copyright 2012-2015 Adrian Smith, 2015-2017 Ralph Irving.
#### SQUEEZELITE BUILDOPTIONS ####
Build options: LINUX ALSA EVENTFD RESAMPLE FFMPEG VISEXPORT IR GPIO DSD CONTROLSBS ALSASYNC BLUETOOTHSYNC
#### AUDIOPLAYER CONFIG ####
### Configuration of Audioplayers
SQUEEZELITE_PARAMETER=-o sysdefault:CARD=b1 -a 80:4:: -v
SQUEEZESLAVE_PARAMETER=-n plugequal
SHAIRPORT_PARAMETER=-d plug:jack
USE_USB_DAC=0
USE_EQUALIZER=0
SYSTEM_USER=pi
GMEDIARENDERER_ALSA_DEVICE=plug:jack
#### SQUEEZELITE -l ####
Output devices:
null - Discard all samples (playback) or generate zero samples (capture)
jack - JACK Audio Connection Kit
pulse - PulseAudio Sound Server
equal
plugequal - Equalizer for plughw:0,0
bluetooth - Your Bluetooth device 00:05:CD:E5:9C:19
default:CARD=b1 - bcm2835 HDMI 1, bcm2835 HDMI 1 - Default Audio Device
sysdefault:CARD=b1 - bcm2835 HDMI 1, bcm2835 HDMI 1 - Default Audio Device
dmix:CARD=b1,DEV=0 - bcm2835 HDMI 1, bcm2835 HDMI 1 - Direct sample mixing device
dsnoop:CARD=b1,DEV=0 - bcm2835 HDMI 1, bcm2835 HDMI 1 - Direct sample snooping device
hw:CARD=b1,DEV=0 - bcm2835 HDMI 1, bcm2835 HDMI 1 - Direct hardware device without any conversions
plughw:CARD=b1,DEV=0 - bcm2835 HDMI 1, bcm2835 HDMI 1 - Hardware device with all software conversions
usbstream:CARD=b1 - bcm2835 HDMI 1 - USB Stream Output
default:CARD=Headphones - bcm2835 Headphones, bcm2835 Headphones - Default Audio Device
sysdefault:CARD=Headphones - bcm2835 Headphones, bcm2835 Headphones - Default Audio Device
dmix:CARD=Headphones,DEV=0 - bcm2835 Headphones, bcm2835 Headphones - Direct sample mixing device
dsnoop:CARD=Headphones,DEV=0 - bcm2835 Headphones, bcm2835 Headphones - Direct sample snooping device
hw:CARD=Headphones,DEV=0 - bcm2835 Headphones, bcm2835 Headphones - Direct hardware device without any conversions
plughw:CARD=Headphones,DEV=0 - bcm2835 Headphones, bcm2835 Headphones - Hardware device with all software conversions
usbstream:CARD=Headphones - bcm2835 Headphones - USB Stream Output
#### SHAIRPORT (SYNC) VERSION ####
3.3.1-OpenSSL-Avahi-ALSA-soxr-sysconfdir:/usr/local/etc
#### OUTPUT SOUND DETAILS CARD 0 ####
closed
#### OUTPUT SOUND DETAILS CARD 1 ####
closed
