Try rollup?

.github/workflows/esm-lint.yml

@@ -1,5 +1,5 @@
 env:
-  IMPORT_STATEMENT: export {default asOptionsSync} from "webext-options-sync"
+  IMPORT_STATEMENT: export {default as OptionsSync} from "webext-options-sync"
 
 # FILE GENERATED WITH: npx ghat fregante/ghatemplates/esm-lint
 # SOURCE: https://github.com/fregante/ghatemplates
@@ -52,6 +52,14 @@ jobs:
           package.json
       - run: npx parcel@2 build index.js
       - run: cat dist/index.js
+  Rollup:
+    runs-on: ubuntu-latest
+    needs: Pack
+    steps:
+      - uses: actions/download-artifact@v4
+      - run: npm install --omit=dev ./artifact rollup@4 @rollup/plugin-node-resolve
+      - run: echo "$IMPORT_STATEMENT" > index.js
+      - run: npx rollup -p node-resolve index.js
   Vite:
     runs-on: ubuntu-latest
     needs: Pack