Thomas, thanks for checking into that. I agree with you; given both the presence of Boot Repair on my system and this otherwise seemingly-inexplicable problem, it is now looking like I must have mixed up my iso files and installed from the Ubuntu Secure Remix when I thought I was installing from the official Ubuntu image. I will report this to the Ubuntu Secure Remix project.
Thomas, thanks for checking into that. I agree with you; given both the presence of Boot Repair on my system and this otherwise seemingly- inexplicable problem, it is now looking like I must have mixed up my iso files and installed from the Ubuntu Secure Remix when I thought I was installing from the official Ubuntu image. I will report this to the Ubuntu Secure Remix project.