I’ve used all of these servers at some time or other and highly recommend them. Unless otherwise noted, they are all either entirely free of cost or offer a free version with substantially useful capabilities. Additionally, they all support secure versions of their respective protocols that work perfectly with free Let’s Encrypt certificates. You can generate and renew certificates easily at SSL For Free.

FreePBX Asterisk SIP PBX
Linux only
(This will probably run in Docker on Windows but I’ve only ever run it natively on Linux. YMMV.)

Technitium DNS Server
Windows and Linux (.NET)

FileZilla FTP Server
Windows only

mailEnable E-mail Server
Windows only

WinGate Caching Web Proxy Server
Windows only

Openfire XMPP Instant Messaging Server
Linux and Windows

LibreNMS Network Monitor
Linux native or Docker and Windows via Docker

NextCloud Cloud Storage
Linux and Windows via Docker

BitWarden Password Management
Linux and Windows via Docker

Simple DNS Plus DNS Server (Paid with trial version)
Windows only