The way the GitHub Action works it does not add sile to the path of the host container. It may be possible to setup a job that does that, but currently only the container based step is supported.

The best way to proceed probably depends on how much other work you need to do in various steps. The most likely two directions I see might be these (but there are other options, if you give me more info about what needs to happen I'll help find a way...)

1. Do your other work preparing the sil files first in other steps, then when the source file is ready to go, call the SILE action with the necessary path(s):

   - name: Prepare sources
     run: make source_file.sil
   - name: The SILE Typesetter
     uses: sile-typesetter/sile@v0
     with:
       args: source_file.sil

2. Use the SILE image as your host container for the runner and install your other dependencies inside it:

   container:
   runs-on: ubuntu-20.04
   image: sile-typesetter/sile@v0
     options: --entrypoint=bash
   steps:
   - name: Install dependencies
     run: pacman -S make
   - name: Build
     run: make

   In this scenario sile will be in the path and usable from your Makefile, but you will be in an Arch Linux container instead of an Ubuntu one.

   This method has the downside of not being able to run other GitHub action "steps" because the entire workflow is inside a docker container.

3. Run the SILE Docker build yourself by downloading the image into the default Ubuntu container yourself:

   container:
   runs-on: ubuntu-20.04
   steps:
   - name: Fetch sile
     run: docker pull ghcr.io/sile-typesetter/sile:v0
   - name: Build
     run: |
       export SILE="docker run --volume '$(pwd):/data' --user '$(id -u):$(id -g)' sile-typesetter/sile:v0
       make

   Of course you'd want to use $(SILE) instead of sile in your Makefile for this arrangement.

If you need more complex tooling, there are more options, just let me know what the needs are.