Mojibake […] is the garbled text that is the result of text being decoded using an unintended character encoding. The result is a systematic replacement of symbols with completely unrelated ones, often from a different writing system.
Failed rendering of glyphs due to either missing fonts or missing glyphs in a font is a different issue that is not to be confused with mojibake.
If the encoding is not specified, it is up to the software to decide it by other means. Depending on the type of software, the typical solution is either configuration or charset detection heuristics. Both are prone to mis-prediction in not-so-uncommon scenarios.
The text file you linked to forces a browser to guess the encoding. Your browser guesses wrong. The file should look right when viewed as Unicode (UTF-8). Your browser probably supports all the glyphs needed to render the file correctly, the problem is not with a font.
A browser may or may not provide an option to change the encoding. I believe Chromium removed such option due low usage, there's an extension though. In Firefox: Open menu → More → Text Encoding → Unicode.
If for any reason your browser doesn't let you do this, then try to view the file outside of the browser. Save the file as-is (with a browser,
wget or whatever software able to download from a given URL), then open it with a text editor able to interpret UTF-8 and force the right encoding if necessary (e.g. in Notepad++: (menu) Format → Encode in UTF-8).