Choose your current and target Keycloak releases to see migration changes and their official guide sections. Add a realm export to find relevant settings.
Upgrade one major version at a time, using the latest patch of each intermediate major. Test and back up before each step.
Rules cover migration notes through Keycloak 26.8.1. Rule texts are in English. Export matches show up to 20 relevant settings per change; not detected does not mean unaffected.
The JSON file Keycloak exported for one realm. It is read in your browser and never leaves it.