How to install a Minecraft Server on a Synology NAS with just Container Manger / Docker Compose.

This how-to uses the incredible docker container available from ITZG. You can google itzg and find his Github and his docker-minecraft-server page. Consider donating to him if this server works out for you.
If you're installing Bedrock, that starts at about 8:50.
For backing up your server's data I would recommend looking up tutorials on how to use Snapshots and Hyperbackup. Both are free, built-in apps which are avaialble in the Synology Package Center.
Also free and available in the Synology Package Center is Tailscale. It's a simple and powerful VPN solution that can make it easy and secure for you to let your friends, family and/or enemies (?) use your Minecraft server from their own homes. You'll have to sign up for an account on their site. Bonus is that you also have an easy way to VPN into your home network. If you're going to use the port forwarding solution on your router, remember to allow that same port through your Synology Firewall. Which should definitely be on if you're opening up your NAS to the WWWs.