Yesterday I wrote a document with many math formulas. Today I updated the software, and now it looks like sh**. What happened here? All the “=” is replaced with a telephone, and that’s not the only sign that has changed. This is not any good for my school homework.
The strange symbols you see are most likely caused by a wrong replacement for a missing font by ‘StarBats’. See also this thread.
The symptom sounds like font problem. Libreoffice bundles itself with a symbols font, OpenSymbol, and it should be installed along with the main program.
I’ve googled a bit, and it seems to be a known bug: Bug #76239
Solution:
A) Manually install OpenSymbol font. Look for the latest opens___.ttf font, download, and install, or
B) Uninstall and reinstall LibreOffice. I don’t know if your personal default settings will be retained or not; I’d avoid this if possible (unless you never did customization).