Problem

The currently specified font-family in scss/_variables.scss results in unreadable pages on some Linux systems. All normal font is exchanged with the according Emojies.

What could be triaged so far

As far as I could see, the problem occurs on Linux systems that have Noto Sans as standard font and neither Arial, Roboto, Segoe UI or Helvetica Neue installed.

Thus the browser will use the Noto Color Emoji font (as specified by bootstrap), but has no fallback font for normal letters. The fallback Noto Sans is not specified in the font-family. This leads to unicode characters that are not found by the browser and then replaced by the next best fitting unicode char (the according emoji).

How the bug can be fixed

Add Noto Sans to the font family in the files scss/_variables.scss in front of sans-serif.

The new font-family would look as follows:
-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Helvetica Neue,Arial,Noto Sans,sans-serif,Apple Color Emoji,Segoe UI,Segoe UI Emoji,Segoe UI Symbol,Noto Color Emoji

Additional data

• Operating system and version: Arch Linux
• Browser and version: Chrome 70
• Reduced test case: Go to any page with bootstrap that does not override font-family (https://artemis.ase.in.tum.de/#/ for example)

Pull request

I'll shortly provide a pull request with the necessary changes.