I had the Same Problem with the URL in the Manual.
The Muse Luxe is shipped with an Bluetooth only Firmware, to use any other Features you have to Flash another Firmware on it.
If you want to use WiFi with your muse Luxe, check out this Forum Post:
https://forum.raspiaudio.com/t/muse-luxe-speaker-with-squeezlite-logitech-media-server/
I tried ESPhome and Squeezelite, my choise is Squeezelite as you can use WiFi/Bluetooth/AirPlay with it an you are to use the “Logitech Media Server” (LMS) to Admin and Control you Muse Luxe.
If you run HomeAssistant, LMS is working fine as inofficial AddOn.
REMEMBER: the USB Cable that is shipped with your Muse Luxe is a “Charge only” Cable - to flash your Muse Luxe you will need an mircoUSB Cable with Data Connection