I think you might be confusing Umami with Plausible? Plausible is a total mess of heavy-idling containers and ClickHouse. I dropped switched to Umami and have had no performance issues of any kind. It's running on ~12 year old shitbox. I do only deal with ~10K events per day max though.
https://github.com/th0th/poeticmetric
Looks interesting but haven't delved in it too much. I do like how I can create specific analytic tracking events without worrying too much about ad blockers but that's hardly unique to Umami.
There's also another interesting analytics open source project whose name I am forgetting. It was written in C or something and was efficient enough to allow free usage or self hosted, it was a simple hit counter I believe.