[KronisLV]

For monitoring servers: Zabbix would work.

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.