Tally is familiar. Growing inventory, multi-warehouse, and operational workflows are not. Migration fails when teams treat ERPNext as a chart-of-accounts clone instead of a new operating system.
Stages that work
Assess and map masters. Migrate and reconcile. Parallel-run critical flows. Cut over with hypercare. Our Spaceki engagement followed this discipline for financials and inventory.
Do not migrate every historical row on day one if it blocks go-live. Bring forward what auditors and ops need; archive the rest with a clear retrieval story.