I was looking for some settings in Firefox to come across this and thought I'd see if it helps solves the problem I experience so much that strains my eyes.
Dimming overlay changed to light overlay by the browser via setting:

Looks like those at Mozilla working on Firefox have done really well here.
An option to control the background which can be very handy for situations where he background of a modal/dialogue has oppositing colours and can overwhelm one's senses if excessively changes. Still don't like the background covered in principle up but I'd prefer that over a dark one (in normal light mode) and I can still read things.
Thank you very much to those responsible for this setting.
Never expected them to do something like this.
Light mode linked to light/white overlays.
Dark mode linked to dimming/dark overlays.
I find that just makes sense if it was done automatically but now manual controls for this implemented in the browser.
Very pleased and happy about this too, twice in two days.
Now hopefully from this point I won't be inundated by flashy overlays with that set to white.
Imagine if it was the the other way round for dark mode users.
Where in dark mode the background turns white instead of darker.
Which is why I thought it might have been a preference set by those working on web design in dark mode and they didn't forsee they effect the rapid screen changes can have for someone viewing their webpages in normal light mode when these modals or dialogues appear as for my reason for starting this poll to find out whether there more dark users than light users.
Quite interesting reading all your views and experiences and I see that everyone's eye conditions are different as for their choice.
Thank you very much