Seconded! We're implementing it at GitLab and while the documentation could use some work, it's been pretty great. Coupled with some off the shelf modeling packages[0] you can get good analytics pretty quick. We even started on CloudSQL (Postgres flavor) before migrating to Snowflake.

[0] https://github.com/fishtown-analytics/snowplow/

Seconded on snowplow. Piwik/Matomo are showing their age, you don't really control your data with Adobe/GA/MixP/etc, and building from scratch seems easy... til it's not. Either use snowplow as is, or at least learn from it to see how they solved issues so you can avoid some basic mistakes (their data QA on input from the trackers, for example, is very well handled).

I built a web analytics system from scratch for my current employer. I give the same advice to anyone that asks.