First thing I thought was simply modifying Chrome default CSS but this is no longer possible as "custom.css" in profile folder was removed in newer versions.
On the Chromium front, someone forked and fixed it at https://github.com/hbtlabs/chromium-white-flash-fix but Chromium never merged it because, quoting the repository:
---
What is the chromium team doing about this issue?
Issue has been logged multiple times since https://bugs.chromium.org/p/chromium/issues/detail?id=1373 Most recent progress is https://bugs.chromium.org/p/chromium/issues/detail?id=470669
The issue has been broken down since they are attempting an algorithmic fix https://bugs.chromium.org/p/chromium/issues/detail?id=21798
Algorithmic fix: determining what's the background color of the current page or theme page then applying it during rendering instead of choosing white by default.
---
And what about Chrome? From the same repository:
---
Why doesn't the Chrome team merge this?
Because it replaces the white by black and most websites have a white background and most people don't use a dark theme. Hence, the white flash is a non issue for the majority of users. Also, the webkit fix changes the background of chrome:// pages to black
---
I also found multiple StackExchange questions on this with many answers providing obsoleted solutions and others which rely on very inelegant hacks, like using desktop automation software to interact in the browser in a really invasive ways.
https://superuser.com/questions/580228/prevent-white-screen-...
I suspect that after "Dark Reader" there will be so many users getting terribly annoyed by this issue and a solution must be found. So with this post I'd just like to raise some attention on this: if your eyes are being hurt by white flashes too, please upvote this post.. We know many Google employees like to hang out around here. :)