try installing ruby manually

.gitea/workflows/pages-deploy.yaml

@@ -40,11 +40,10 @@ jobs:
           ref: 'pages'
           path: 'pages'
       - name: Setup Ruby
-        uses: ruby/setup-ruby@v1
-        with:
-          ruby-version: '3.3.5' # Not needed with a .ruby-version file
-          bundler-cache: true # runs 'bundle install' and caches installed gems automatically
-          cache-version: 0 # Increment this number if you need to re-download cached gems
+        run: |
+          apt-get update && \
+          apt-get install ruby-full build-essential zlib1g-dev -y && \
+          gem install bundler jekyll webrick
       - name: Build with Jekyll
         # Outputs to the './_site' directory by default
         run: bundle exec jekyll build --destination pages