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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.
Here's one I designed as my first electronics project: https://github.com/tadfisher/nyx-kb
Seems to meet your criteria, but obviously requires some assembly.
Pretty much all the options are covered here:
https://github.com/diimdeep/awesome-split-keyboards
Lily58 is a popular minimalist split keyboard
NOTE:
The number of mentions on this list indicates mentions on common posts plus user suggested alternatives.
Hence, a higher number means a more popular project.