phein4242B

See this howto: https://poolp.org/posts/2019-09-14/setting-up-a-mail-server-with-opensmtpd-dovecot-and-rspamd/

I have delivery to the inbox of all major providers using this. Email is not that hard…

Alma, Talos, OpenBSD

I run unattended-upgrades on all the debian/ubuntu deployments I manage. One of the deployments even has automatic reboots enabled. I still do major upgrades by hand/terraform, but the process itself works flawless in my experience.

OpenLDAP multi-master with a bunch of custom schemas.

Can you explain what you mean with lightweight?

SCO OpenServer

See a search engine and do some research. Maybe try out a bunch of different distros and find out for yourself

You expressed yourself just fine and my question is still valid. Do you have the capacity to handle multi Tbit traffic on the edge ips that you use to hide the backend ips? Because if all of those are flooded, not only will the backend app be unreachable, but all your customers will be unreachable as well.

We have a bunch of these at the hackerspace. They run vanilla debian and connect to a terminal server using xdmcp. Works like a charm.

You will be in for a surprise once you learn about tcpdump ;-) Welcome to internet hosting!