This seems like a pretty cool project!

Currently using Apache Skywalking myself, because it's reasonably simple to get up and running, as well as integrate with some of the more popular stacks: https://skywalking.apache.org/

I do wonder how ClickHouse (which Uptrace uses) would compare with something like ElasticSearch (which is used by Skywalking and some others) and how badly/well an attempt to use something like MariaDB/MySQL/PostgreSQL for a similar workload would actually go.

I mean, something like Matomo Analytics already uses a traditional RDBMS for storing its data, albeit it might be an order of magnitude or two off from the typical APM solution.