The problem with running from C: is that Windows 10 is preventing anything from being run from C:. I’m getting the error "Error opening installation log file. Verify that the specified log file location exists and is writable.
Fortunately this lead to a discovery, there was a key in my registry that was pointing the installer to a drive that no longer exists, so I fixed that. But it’s still giving the error about the folder containing invalid characters. ><
I also deleted C:\ProgramData\Epic just in case.
I was able to get the log file to save to my external harddrive and I’ve uploaded the txt to my dropbox: https://www.dropbox.com/s/ok6oone5wjq8o8a/EpicGamesInstallerLog.txt?dl=0