The version that Keycloak comes with doesn't know how to form URLs to download ARM64 distributions of Node. By upgrading it, it downloads the appropiate Node version built for ARM64.
diff --git a/themes/pom.xml b/themes/pom.xml
index 2502cbea7d..b09e5bac74 100755
--- a/themes/pom.xml
+++ b/themes/pom.xml
@@ -37,6 +37,7 @@
<plugin>