On my notebook, when I start the system installation, I press F10 so that systemd:backlight doesn’t fail, and everything runs fine. But is this a bug or an issue with the notebook itself?
Impossible to answer with no information.
http://www.catb.org/~esr/faqs/smart-questions.html#beprecise
I’ve made jokes about systemd being large, but does it really have its own backlight control? That’s kind of interesting and wild 
Having to press F10 isn’t anything I’ve ever had to do on a laptop, my backlight always worked fine, and it sounds like a bug. I suspect figuring out a better way to hook the backlight up to Linux/GPU driver (like i915.enable_dpcd_backlight or forcing a Windows OSI with acpi_osi=Windows 2017) might indirectly solve that.