Been running Unraid for almost a year. I was previously running Windows with nearly zero insight into the health of my apps, RAID, etc. Made me very nervous. Unraid makes it all so easy.
I'm running many of the apps you mentioned and the implementation of docker on Unraid is easy to install, update, etc. I used docker on Windows but it was not the same. I'm not a software dev, so I'm not sure why you said Unraid's docker implementation is hacky. It seems good to me.
The reason I switched to Unraid was I had to add more storage to my RAID and that was impossible in Windows without destroying the RAID and losing my data. I considered TrueNAS, but my understanding is the same is true. They're supposed to be adding that capability soon ™️ but who knows when that'll actually be available and reliable. Unraid let's you add more storage whenever and the drives don't have to match. I love the flexibility.
I use Nginx Proxy Manager docker to access my apps externally. My SO is not tech savvy and after setting up the individual apps with the domain I have, it's usually smooth sailing. If I ever need to do any mucking about with the server itself, I turn on UI teleport. I also have a PiKVM but have only needed to use it a couple times. It's just not necessary with how reliable Unraid is.
My server has an i5-6600 and utilizes QuickSync, which is great. More energy efficient than a dedicated GPU. I've considered adding a GPU but I haven't run into a situation where I need it.
Tldr: highly recommend Unraid.
I tried Flex Launcher on RebornOS but couldn't really get it to even launch stuff, besides the Plex app. Maybe I need to read the documentation better. I think it's promising but has a steep learning curve. I don't need it to hold my hand the entire setup but would like a little more help with configuration than it currently offers post install. My issues could also be due to Linux. I haven't tried the Windows version.
This is basically what I do, except the quicker way without using ADB to remove anything. Might try removing the junk though to see if it makes a difference. Launcher Manager and Flauncher makes an Onn 4K very snappy. Hard to beat for $20 and a little setup effort. I used to use Firesticks for years, but they get so slow and constantly revert my launcher changes. Finally got rid of them all.