Accessibility block's plugin page https://moodle.org/plugins/block_accessibility
User tours' documentation page https://docs.moodle.org/35/en/User_tours
Install the Accessibility block plugin, and go to a page with a User tour set.
Add the Accessibility block and press the "Launch ATbar" button.
Try to use Text-to-Speech with the User tour messages.
The TtS button would be clickable without affecting the User tour message.
Or that the text would be narrated without having to press the button again.
The text is not auto-spoken and you cannot click off the message for the TtS button.
User tours exclude the use of tools offered by the Accessibility block and ATbar:
if you click off or close the message, it resets the User tour.
Edit: workaround is to turn off backdrop, as pictured. However this is sub-optimal for redirecting users' focus.
I am testing on Mozilla Firefox Quantum 66.0.3 (64-bit) and Mozilla Firefox Developer Edition 67.0b9 (64-bit).
Also Win10, on Moodle 3.5.5 (freshly upgraded from 3.5.3 where this was first a problem), in Boost theme with some custom CSS.