Another option is to use duti (https://github.com/moretension/duti).
Run brew install duti
, save a filetype like this as:
duti -s com.sublimetext.34 public.plain-text all
The changes should be applied immediately, so you don't have to restart like when editing com.apple.LaunchServices.plist
.
To also change the default application for executable scripts with no filename extension, add a line like this:
duti -s com.sublimetext.34 public.unix-executable all
Some files are also considered 'public.data', not 'public.plain-text', so you can do this as well:
duti -s com.sublimetext.34 public.data all