Poor man's dashboard: Get your desired metrics with grep/wc/whatever shell commands from your logs, and visualize with PyQtGraph/PySide (or even gnuplot, for an even lighter experience).
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> GoAccess is written in C
I assumed it would be written in Golang from the name.
For APM across some popular stacks: Apache Skywalking might be worth a look (though probably with PostgreSQL instead of ElasticSearch).
For analytics: Matomo is good.
For uptime monitoring: Uptime Kuma is really good.
Consider a separate cheap VPS for the monitoring stack, whatever it might end up being, like something from Hetzner.