Where to begin?
I have a functional HA Core setup running on my Synology NAS (920+) right now. Good times. I can turn my stuff on and off from my iPad! 
Woohoo! It’s actually working WELL.
Except… not all is well. I have a separate IoT vlan (one way mirror, the main LAN can see into the IoT vlan, but not the other way around), and while many things seem to have no problems working perfectly, other things have been incredibly obnoxious. Most of my HomeKit stuff is fine… but some is not. None of my Aqara sensors (or my hub for that matter) work. Tons of threads discuss people dealing with the same issues, especially where vlans and Aqara (and a lot of other ZigBee stuff is concerned), so at least I know it’s not just me… but the solutions mostly seem to be pretty intense.
And then… extending HA is a thing. Only having the Core install in Docker seems to complicate everything. All the online guides say “yeah just click here to install HACS and install MS Visual blah blah for easy editing and…” and I can’t do any of that with the Core install. I guess there are ways of spinning up additional Docker containers and linking them, but yeesh. That’s “better” that just installing the Supervised version in the first place? Why? Processing power? Disk space? Sheer geek bragging rights for the number of days spent hunting through tutorials vs watching some YT videos to get the same task done? I’ve not seen the downside of running the Supervisor mode in a Docker clearly explained, yet, TBH, other than the main site’s guides all only offer Core for Synology. Especially confusing when I found a guide online that seems to do just that: Install HA Supervised into a Docker container. What’s the downside?
Ignoring that and going back to the VLan thing, the solution most seem to have found that works the simplest is to just give HA a second network interface directly on the IoT vlan. Not 100% ideal from a security standpoint, but… I don’t think it’s terrible, either. Except, of course: Following the main HA site’s instructions for installing this Core install into Docker put the networking in Host mode. Easier, yes! But not when vlans start getting involved. I’m honestly I’m not entirely sure how to pass both the main LAN and the IoT LAN to the Synology over the one network connection (technically 2, it’s a bond, but still), using my UniFi gear (which is mostly great, but there are occasionally areas of Ubiquiti stupidity such as the multicast routing that might solve the Aqara issue just not working right). Not that I’ve gotten past the “need a second network interface in Docker but it’s in Host Mode now” hurdle. I could rebuild it in Bridge mode, maybe? But I recall seeing lots of threads discussing issues getting things passed back and forth correctly when the containers are in Bridge mode, too, so perhaps that only leads to different problems?
And now, perhaps a more philosophical question? I have home automation working pretty nicely, overall, in HomeKit, my current platform of choice. But I really love the idea of being 100% functional offline, local processing, etc, in HA. And the multi-vendor aspects appeal, too. While the vast majority of my gear is HomeKit native, I do have a few things that aren’t, like my UniFi Protect cameras (which bridge nicely to HomeKit via HomeBridge, installed on an old MacMini), and my Bond ceiling fan controller (which does Google Home and Alexa, but not HomeKit, and I won’t allow either of those two in my house), which are pretty key. So nearly everything is in HomeKit. The Bond even partially loops back to HomeKit, from HA’s HomeKit integration.
Given that, is it better to pass the HomeKit stuff that’s already up and running into HomeAssistant (which is what I’m doing now, for at least some things… except I get duplicates because HA detects stuff on it’s own, too), OR should I instead delete everything from HomeKit and install directly into HA, and then link back to HomeKit from there for control via Siri and such? That’s the only way, I assume, to have it all work without duplicate entries for everything, one from HK and one from HA. And Of course I want to be able to do things from outside the house, too. Local control is only awesome when you’re local. What’s the best way to go, do you suppose?
Or do I punt, and try to stay HomeKit native as much as possible. I can make the cool iPad dashboard I want using something like Viz-Designer… probably not as flexible as HA themes, but I’ve seen really nice uses of that. Probably the easiest way, and just punt on all this complicated stuff, but it feels like cheating, and I feel like I’ll still likely hit it’s limits sooner than later.
Sorry for the rants. But this “easy” and powerful program is driving me batty… probably why I gave up on the first time I played with it, years ago. I swear I’d consider hiring someone to do the base setup of this stuff if I could handle it all turn-key from there… That said, if anyone here still wants to try to help, I’d be ever so grateful. 
It it helps, here’s the rundown of the obscene amount of random smart home stuff I’ve accumulated over the past few years as I’ve gotten more and more into this:
Working great in both HK and HA:
- Lutron Caseta switches and the Lutron Bridge (on IoT vlan and yet seen without issue)
- Philips Hue smart bulbs and the Hue Hub (and a switch of theirs) (on house LAN… I’d love to move it to IoT but I couldn’t get it working there)
- UniFi Protect cameras (via HomeBridge) (on house LAN… I’d love to move it to IoT but I couldn’t get it working there)
- Various TVs and stereo receivers (on house LAN, mostly via HomeBridge, all blocked from internet access)
Not working in HA, but works fine in HK:
- Aqara temp sensors, door sensors, and motion sensors, via the M2 hub (on IoT vlan)
- Vocolinc smart plugs, bulbs and LED light strips (HomeKit native, all on IoT network)
- Meross smart plugs (HomeKit native, all on IoT network)
- WeMo smart plugs (HomeKit native, all on IoT network)
- KooGeek smart plugs (HomeKit native, all on IoT network)
- SwitchBot smart plugs (HomeKit native, all on IoT network)
- Onviv Temp and motion sensor (HomeKit native, all on IoT network)
Only works in HA (and native app):
- Bond fan controller
HomeKit stuff is routed mostly through my AppleTVs, I believe, although I recently added a HomePod Mini.
I’d love to get rid of all of the vendor-locked hubs, too, eventually, but everything I’ve seen has indicated that in particular, the three that I have (Lutron, Hue, Aqara) tend to be the only way to reliably work with their specific gear, as opposed to something more general and universal like a Conbee adapter. (and, of course, attaching such a USB dongle to a Synology NAS presents extra challenges, too sigh)