try this?

.forgejo/workflows/publish.yml

@@ -21,7 +21,7 @@ jobs:
       with:
         maven-version: 3.9.9
     - name: build with maven
-      run: mvn --batch-mode --file pom.xml package
+      run: mvn --batch-mode --file pom.xml -Drevision=${GITHUB_REF_NAME/v/} -Dkeycloak.version=21.0.0 package
     - name: copy ears
       run: |-
         mkdir -p release/ears

pom.xml

@@ -47,7 +47,7 @@
     <maven.compiler.target>1.8</maven.compiler.target>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <github.account>lucafilipozzi</github.account>
-    <revision>1.0.9</revision>
+    <revision>${tagged_version}</revision>
     <keycloak.version>15.0.2</keycloak.version>
   </properties>