I have an occupational need for about seven different keyboards including US, Greek Polytonic, Classical Hebrew, Ethiopic, Semitic Transliteration, and extended Latin keyboards (college professor). But I have had a devil of a time with High Sierra. Custom Keyboards that I install (ones that worked just fine in earlier OSs) don't stay accessible in the input menu, and disappear from the input sources menu. I have tried various fixes, to no avail. NOW, I've tried to pare it back so that I have no custom keyboards installed at all, just the native US keyboard entry. But my input menu lists multiple duplicate copies of keyboards that the system preferences doesn't even acknowledge are installed! HELP. Apple has to fix this issue.
These are my current input sources dialog (System Preferences > Keyboard > Input Sources) and my current input menu drop-down (Menu Bar upper right).