Software Selection and Packages for Homebult Server

I currently have three Synology NAS machines with oodles of storage space, plus another one which I purchased for my church. I also have a couple of web sites; one in particular which has been up for over a decade is Streamliner Schedules. I had been shared hosting with IX, but after I got hit with a $500 renewal bill (for three years) plus an unannounced migration to a poorer hosting plan (only one IP; I had been receiving 8...messed my DNS up completely on everything but the main site) after IX sold out to EIS/Site5 (with their legendary customer service) I elected to self-host for the present using my Synologys. I do have business-class internet service with static IPs at the house and, after the DNS problems were taken care of, I've had no complaints from my visitors.

I've been self-hosting my own email servers for about five years now, again using the Synologys, but now that I have some time to play with the old web site I wanted to work on migrating it to a modern CMS system such as Drupal. While Synology machines can host Drupal, their semi-proprietary operating system (DSM 6, based on Linux) has a lot of limitations such as installing PHP extensions and makes it difficult to use Composer and Drush. Plus, my machines each have only 1GB RAM, non-expandable, which seriously limits the number of process threads available. After a weekend of tearing my hair out, I started seriously thinking about a hardware upgrade.

At some point I'll probably use a Digital Ocean droplet or similar as a mirror server, but I'm kind of funny about wanting to have data which is important to me personally stored on my own hardware on my own property. I did a little online shopping and now (well, in a couple of months after I start getting a steady paycheck again) I'm seriously planning to put together a personal server system built around a Supermicro H8SGL motherboard and 1U rackmount case. My question regards assembling the software suite for it.

I know that I do want to set it up as a Linux server, although I'm still not completely comfortable with Linux (I have an older desktop running Ubuntu 18.04 LTS). The primary function will be as a web server, but I also want it to handle email and DNS (preferably with DNSSEC). My Synology machines are good for offline data storage, so that would be a minor role. But I also want to use this new machine as a testbed to get familiar with new packages and techniques and to expand my skill set in general. (It would be nice to be hired for something besides plunging toilets and changing light bulbs!)

So if someone out there is familiar with provisioning and using Linux servers and can point me to some resources, I would appreciate it. Again, I'm not in a big hurry on this, but I do want to start moving in that direction.