Black screen on non-WM x11 and crash on LightDM (Fedora)

I'm developing and maintaining a LightDM Greeter for Linux, which uses QtWebEngine (with Python) to allow the usage of web technologies to create wonderful themes. It's called web-greeter.

LightDM crashes

Recently, RootVoid created an issue where they describe a program crash with LightDM in Fedora (see log below), but it works without any issue when logged in inside a Window Manager or Desktop Environment.

(Web Greeter Log Image)

As the log shows, the program just stops with the next message: sys_chroot("/proc/self/fdinfo/") == 0, which occurs when executing: QWebEngineProfile.defaultProfile(); check here. No Python error, no X11 error, it just crashes.

By the way, web-greeter works on Ubuntu and Arch without any issue, this only happens on Fedora for some reason.

Not working on non-WM X11

After identifying the error, I tried to check and reinstall all the related Fedora packages, also with PIP with root privilegies, but none worked. Then, I tried to run web-greeter with a simple X11 server, and it didn't work as well, but this time because of a different reason: black screen... why? Idk.

Inside a tty in Fedora, I ran xinit xterm and then web-greeter --debug in xterm. This time, it didn't crash, but WebEngineView only shows a black screen, also with DevTools.

Check the attachment video.