Yeah CleanMyMac is really good at uninstalling, it even has a tool for rooting out rogue prefpanes and orphaned pkg leftovers.
I wish you had checked if Quarantine was applied to the kexts / prefpane. If so, we must update the solution with the uninstall action step (because manual un-quarantining is boring and about a dozen extra commands). Most people keep Gatekeeper on, unlike myself.
So it’s about an expired cert. Like I guessed, pkg’s with expired certificates might be unable to install even if already installed kexts/apps will continue running in an expired state unless explicitly put on the blacklist by Apple.
Please confirm this so that we no longer call the date trick an optional extra step but rather mark it as mandatory.
Safe mode is the easiest way of enforcing VESA over web drivers and that’s the sole reason why I recommend it. I still don’t know if you can (re)install the driver package while Safe, we need someone to confirm.
You definitely should find a way to install 17G1404, I can hardly believe that even if you have to run a heavily doctored out-of-spec system there’s no way to patch the latest installation image — even if incremental updates are legit impossible in your scenario. So far you seem beating about the bush and wasting your time. Stay away from the ‘Swiss Army Crutch’ sort of apps like the one so heavily featured in your posts, they all tend to do more harm than good.
As someone from the hackintosh crowd I also recall both are extremely sensitive to hardware acceleration. So maybe they are freaking out because VESA mode offers none? Like shutting down randomly and such like stuff. They also won’t work while time/date is incorrect. Same for iMessage, FaceTime, etc.