Tsss... if you have read the thread until the end, it turned out it was just a window manager problem in linux combined with the video card driver, it was fixed in git, but not in any official binary yet (at least for what I could test, this guy didn't reply to say if tests on his side were ok, that's why the issue is still opened).
2ndly as I already told you, I can't reproduce your white screen here on my desktop, it happens only in windows and I had it a long time ago while setting up the 1st versions using sdl2, but I have not seen it since then here. So I believe it's more related to some video driver/video card issue, and anyway since it can be worked around easily and is impossible to reproduce for me for now, there's no point.
For the notifications I had telegram but only in linux, I downloaded the windows one, and in the parameters screen for notifications you can simulate notifications on your screen, that's what I did, raine playing in the background visible, the telegram window on top and the notifications which appear when you move the mouse over their displayed screen. No blinking, no white screen, nothing. Well since you use something to also capture some video, maybe it doesn't help.
Why is everybody thinking this "real fullscreen" is like a super holy solution ? The only reason previously to have this "real" fullscreen was because that was the only way to have double or triple buffered display, it's not the case anymore with sdl2 it works perfectly in a window. So this fullscreen windowed mode gives a few advantage, you can't display a window on top of something using this "real" fullscreen, here you can without any problem which makes things easier for debuging or checking something else. The windowed fullscreen is actually a better solution, especially for lcd screens, the real one tries to change the screen resolution to match the window size, you don't want to do that on a lcd screen, that's why version 0.50 was created, and it was a very long time ago now...
In the end, this is something really easy to test by modifying the source and testing by yourself, too bad you don't compile, you would have seen by yourself it's not the right solution ! Sorry about your driver glitches, but I can't do much about that, as far as I know at least... !