My pyglet application fails to run, only giving the error ImportError: Library "GLU" not found. I have installed PyOpenGL and libgl1 across the system, in the virtualenv, and tried reinstalling everything multiple times. Nothing seems to help. Similiar questions mention it may be related to my graphics card, which is Intel Corporation HD Graphics 5500 (rev 09). Anyone have any ideas?
Further details

Python version: 3.7
IDE: Pycharm Community
OS: elementaryOS v5.0 Juno
Installation method: Flatpak
Graphics Driver: Intel Corporation Broadwell-U Integrated Graphics
Don't install pycharm through flatpak, for whatever reason that doesn't work. Install it through the pycharm website.
Pyglet fails to load GLU library