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InfluxDB
Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.
https://komga.org/ is another good alternative. I wouldn't count on native support in Jellyfin anytime soon, there's a long way to go with ebooks and they're quite a bit simpler.
NOTE:
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