There's no such thing as accessibility. Accessibility is just usability.
Toasts have poor usability because its easy to miss them. This makes them bad for everyone, regardless of screen reader.
This is not strictly true some accessibility choices can harm usability for those that don’t need that affordance, if it is not configurable.
This is not strictly true some accessibility choices can harm usability for those that don’t need that affordance, if it is not configurable.