I'm looking for a NAS for a very long time (budget, size, network, etc.), but when I was ready to pull the trigger on a Synology, they did this, and I dodged a bullet.
Long story short, I'll be buying an ASUSTOR AS6804T, and if I don't like the software, I'll just install TrueNAS on it. It's not only officially supported, they have a full length video showing the process. They don't provide tech support, but eh.
Icing on the cake? The eMMC storing the original firmware sits on its own USB port, so you disable that port, and both disable and protect the firmware from being overwritten.
If you want to return to original firmware, enable the port, remove the TrueNAS SSD, and viola!
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