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letsdebug
Diagnostic tool/website to help figure out why you can't issue a certificate for Let's Encrypt
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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.
They list no stipulations about prohibited certificate uses[1]. Their restrictions on domain uses seem to be mostly tied to legal requirements (not issuing for sanctioned countries, for example). It's all also pretty transparent, from what I can tell[2][3]. Certainly more so than a normal CA.
[1]: https://letsencrypt.org/documents/isrg-cp-v3.3/#1.4.2-prohib...
[2]: https://letsdebug.net/
[3]: https://github.com/letsdebug/letsdebug
NOTE:
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