Map the Amplitude behaviors your teams actually reach for, not the screens they recognize. The hard parts are event semantics, identity resolution, cohort definitions, funnel logic, and the governance around who can create or change a metric, and a replacement has to match your product questions before it matches every chart type. It also helps to be honest about depth. PostHog is the closest match to Amplitude, pairing event-based product analytics, session replay, feature flags, and experiments in one self-hostable stack. Countly sits in the middle, a self-hosted product-analytics and engagement platform with event, session, and crash tracking and mobile SDKs, closer to Amplitude's behavioral focus than to plain web stats. Umami is the lightest of the three, a cookie-free tool better suited to traffic and conversion than deep behavioral exploration.
Expect gaps in self-serve breadth. Amplitude is tuned for non-SQL product exploration - fast funnel slicing, path analysis, reusable cohorts, and collaboration around saved analyses - and an open source move may ask for more schema discipline or more engineering involvement. Some teams accept that because they want raw event ownership and predictable infrastructure. The piece people most often miss is not a chart type but the shared metric layer that keeps product, growth, and support teams arguing from the same definitions.
The move usually begins with a historical export from Amplitude, a backfill into the new store, and a period of dual-writing from your SDKs so you can compare the same production traffic in both systems. Raw events, timestamps, event and user properties, and identifiers can survive if you export them carefully; dashboards, notebooks, saved cohorts, and permissions are application objects you will mostly rebuild and validate. The real cleanup is identity mapping, timezone handling, deduplication, and reconciling new funnel counts against the Amplitude baseline before anyone depends on them.