A frustration-free, working recipe for LibreOffice on the heroku-16 stack, after a lot of trial & error. Particularly useful if you use the libreconv gem for document conversion to PDF in Ruby on Rails applications, and results in a much smaller slug size (which will likely keep you under heroku's soft limit as an added bonus) when compared with other options.
Add the heroku-buildpack-apt buildpack to your project:
heroku buildpacks:add --index 1 https://github.com/heroku/heroku-buildpack-apt.git
Add our LibreOffice buildpack to your project:
heroku buildpacks:add --index 2 https://github.com/BlueTeaLondon/heroku-buildpack-libreoffice-for-heroku-16.git
Optionally, add the following buildpack, which provides a handy combination of fonts for LibreOffice to use:
heroku buildpacks:add --index 3 https://github.com/debitoor/heroku-buildpack-converter-fonts.git
Create an Aptfile file in your project root with the following content:
libreoffice
libxfixes3
libxinerama-dev
libxinerama1
libxdamage1
libglu1-mesa:i386
Redeploy your project after committing the above file.