[UI/UX] High-contrast theme still missing

I’m currently evaluation ERPnext. One major issue show up immediately when logging in: the contrast is far too low. While there have been several posts about this issue even back in 2017, I did not find a solution.

How to increase the contrast or the UI in the online-demo?

Hello all, any chance this post gets some insight from the community?
I also got comments from users about low contrast issues. I tried with some custom themes made by a contributor of this community but could not get them to work. Also tried with a tool named Full Size (?), with same unsuccessful results.
Any help will be appreciated. Thank you.
I’m running ERPNext: v13.0.0-beta.14 in Linux Ubuntu 20.04.