S3 - tebi.io
Emails - mailgun or postmark
Analytics - ackee (open source, self hosted, easy to setup), matomo, piwik
Observability - grafana, loki, elastic search (open source, self hosted, soon to be part of bootsaas starter), new relic, datadog
VPS hosting - Contabo (cheapest - 4.5eur for 6gb RAM, 4vcpu, 32TB traffic out, unlimited in)