Polyglot breaks at least one existing filetype.
I'm using vim-outliner plugin. When vim-polyglot is installed, filetype for *.otl files (used by vim-outliner) is empty. Putting let g:polyglot_disabled = ['ftdetect'] in my vimrc brings things back to normal, the files are again of expected votl filetype. Looks like polyglot is doing something funky with filetypes.
I've noticed the same issue with *.lean files (used by the Lean programming language).
I had the same issue for *.lean
I experienced the same with *.slm files. Using :lua vim.filetype.add(... wouldn't cause the filetype to be updated. I need to disable polyglot's ftdetect but that would cause *.coffee files not to be recognized.
Per #871 this plugin also BREAKS Justfile support as shipped in current VIM and Neovim releases. This is something that needs to get addressed or this otherwise great plugin will quickly become an anti-pattern. In #872 I've offered a path forward to get some of the urgent bits dealt with and hopefully get some longer term attention. Here is to hoping @sheerun is willing to let it get some TLC soon!