Not a real answer to this, but I've experienced this font issue in at least 3 of my Windows 10 laptops/PCs.
Things common to all those PCs, if I remember correctly, were:
- Windows 10, drivers, Chrome, and all software up to date.
- Copy of Roboto font family (downloaded directly from Google) installed locally.
- Font issue was noticeable not just on Android SE, but even on Google's sites using Roboto.
Issue was gone once I uninstalled the font family from my system. I suppose it was a Chrome-specific issue where the local Roboto family competed with the Google fonts' online version of it.
This could be relevant to Ubuntu as well.