We only use Xeons on developer desktops and production machines here precisely because of ECC. It's about 1 bit flip/month/gigabyte. That's too much risk when doing something critical for a client.
ECC is supported on most Ryzen models, as long as the motherboard supports it. In fact, ASUS and ASRock (possibly others) have Ryzen motherboards designed for workstation/server use where ECC support is specifically advertised.
 The only exception is the Ryzen CPUs with integrated graphics.
ECC is not disabled. It works, but not validated for our consumer client platform.
Validated means run it through server/workstation grade testing. For the first Ryzen processors, focused on the prosumer / gaming market, this feature is enabled and working but not validated by AMD. You should not have issues creating a whitebox homelab or NAS with ECC memory enabled.
ECC support not being "validated," for all practical purposes, simply means that board vendors can advertise a board lacking ECC support as compatible with AMD's AM4 platform, without getting a nasty letter from AMD's lawyers.
However, I use only computers with ECC, previously only Xeons, but in the last years I have replaced many of them with Ryzens, all of which work OK with ECC memory.
When having to choose between a very small risk of losing the price of a CPU and having to use for sure, during many years, an Intel CPU with half of the AMD speed, the choice was very obvious for me.
The latter is a big problem, one of the extreme-OC guys (Buildzoid) who interacts frequently with the OEMs (as he is pushing their stuff to the limit and he frequently needs their help) has commented that AMD has a really bad problem with their BIOS teams. The AGESA firmware (the low-level code that the processor actually runs) is buggy as all hell at a firmware level and the OEMs are forced to patch around it in BIOS, but the AGESA firmware also has a massive problem with code churn, so these BIOS fixups basically stop working all the time. And the driver teams at a lot of OEMs are literally one person, so there isn't enough staffing there to test everything all the time. Long and short of it is: stuff breaks in AMD BIOSs, constantly, and they don't notice it.
This is obviously a huge problem when ECC is not an officially supported feature, because it means nobody is testing it! You might update your BIOS (as you frequently have to do with AMD machines) and suddenly ECC stops working, it might be running ECC in non-ECC mode and no longer correcting errors. Or it might have screwed up reporting them to the OS.
The server/workstation boards are the only ones you should be trusting Ryzen with ECC usage on.
That's not true. There are Core i3, Atom, Celeron, and Pentium SKUs with ECC. E.g. the Core i3-9300
That's an extreme claim. Why do you say so?