Is stream ingestion with Upsert compatible with the RealtimeToOfflineSegmentsTask? I plan to have a realtime table that uses the upsert functionality, and then have older segments moved to an offline table to make a hybrid table.

No, they do not work together

So there's no way to move data from an upsert enabled RT table to an offline table?

@User today you can do so, as in, Pinot won’t stop you. But upserts will be limited to real-time table only

Ah ok. I may have misunderstood the original question.

Let me clarify - Upsert functionality is limited to realtime-only tables. If you did have an offline table as well (in case of managed offline flow), then upsert functionality won't work across realtime and offline. But if users were OK with this limitation, as in limit upsert to the realtime part, then they can use it in that mode (there are cases doing so).