Óbuda Museum is a local-history museum in Zichy Palace, covering the older town that became part of Budapest in the 19th century. Its collections include furniture, household objects, workshop tools, clocks, ceramics, textiles, badges, music material, and city-history exhibits.
It is most useful if you are already exploring northern Buda or visiting Aquincum and want context for Óbuda beyond the Roman ruins. The permanent exhibition is accessible for disabled visitors.