With Godot browser version is not yet accessible friendly out of the box. But btzr has been working on an addon for a long time for this: https://github.com/btzr-io/godot-aria
Alternatively, I think the TTS can be used to speak text: https://docs.godotengine.org/en/stable/tutorials/audio/text_to_speech.html#basic...
ORCA works with live regions and buttons, sliders, etc. for me, It reads the accessibility_name or button text. I'm not sure about non-interactive nodes like labels that don't have accessibility mode set. I ended up using a live region to get any screen reader to read out the text I want it to.