Hi. Not sure, but in "windows" there is option to have Dark theme. Also, in the Google Chrome web store, there is an extension or app that inverts web pages to high contrast. And there are a few Linux distros made specifically for people with vision problems. Hope this helps somewhat.

Yes, deepin use Lightdm, so you have to search about accesibilitty on debian and lightdm

Here is:

https://wiki.debian.org/accessibility#lightdm_accessibility