Rev 3/9/18 (see Revisions)
My motive for experimenting with manually creating flash drive installations (which turned out to be a failure in many cases, due to boot-process subtleties which are over my head) was that I had tried Etcher (after trying every other major USB-installer that runs on Linux) and concluded that there is no reliable USB-installer that runs on Linux.
However, it appears that the problem was that I was using a live installation to run Etcher, and to run Brasero for purposes of generating ISO's (from bootable DVD's) to use as inputs for Etcher. Since switching to a full installation of Linux Mint for these tasks, Brasero has so far produced error-free ISO's from bootable DVD's, and Etcher has so far handled everything I've thrown at it, except Ubuntu 1510, perhaps due to a problem with the ISO (it was able to install Ubuntu 16.04 and 17.10). However, Startup Disk Creator (SDC) in Ubuntu 1710 was able to install 15.10, and it boots (it also works on Debian and Ubuntu-derivatives, although it won't recognize ISO's with certain types of problems). I don't know why Etcher failed in this case, but the important thing is that I was still able to perform the installation without using Rufus and Windows.
Notes
Revisions
3/9/18 - Added reference to my experience with attempting to install Ubuntu 15.10.
