x86 based ubuntu migration to graviton (t3a.xlarge t0 t4g.xlarge)

Minimal change to system will be hard to achieve here: different instructions set at h/w level means different binaries for the whole stack. But, your Java jars will remain identical. On data side, you may want to use DMS to migrate quasi transparently (DMS can run will application is running). You may also consider RDS / Aurora serverless (which is pay as you use) to be able to use a smaller graviton instance.