@clag I believe that flymake or flycheck is integrated by default with lsp-mode. I’m not an expert at all the emacs packages but I do get compilation warnings and credo warnings with lsp-mode, and I’m fairly sure that happens via flymake (or maybe flycheck).
Yes I am. Sorry, looks like I missed another step in the wiki! Currently, in order to use the lsp layer (which uses lsp-mode) you need to be on the develop branch of spacemacs (your ~/.emacs.d should be on the develop branch). I’ve added this to the wiki now 
