We have to use modern yarn

Dockerfile

@@ -32,6 +32,9 @@ ENV PATH /usr/local/node-${NODE_VERSION}/bin:$PATH
 ENV RAILS_ENV production
 ENV NODE_ENV production
 
+# will install yarn
+RUN corepack enable
+
 # renovate: datasource=github-releases depName=tootsuite/mastodon versioning=semver extractVersion=^v(?<version>.+)$
 ARG MASTODON_VERSION=4.3.0
 
@@ -41,13 +44,8 @@ RUN curl -L https://github.com/tootsuite/mastodon/archive/v${MASTODON_VERSION}.t
     bundle config --local set silence_root_warning true && \
     bundle install && \
     bundle clean --force && \
-    rm -rf ~/.bundle /usr/local/bundle/cache && \
-    yarn install --pure-lockfile
-
-# secret keys are not built into assets, so precompiling is safe to do here
-# (these variables are required by rake though)
-RUN SECRET_KEY_BASE=insecure.secret_key_base OTP_SECRET=insecure.otp_secret \
-    bundle exec rake assets:precompile
+    rm -rf ~/.bundle /usr/local/bundle/cache
+RUN yarn install
 
 # https://github.com/rubygems/bundler/issues/5245 means that bundle exec writes to Gemfile.lock
 RUN ln -fs /run/mastodon/bullet.log /app/code/log/bullet.log && \