X470D4U CPU and Memory compatibility

Hi, I'm interested in using the X470D4U in my homelab vm host/nas build but am getting conflicting compatibility information from online sources and PC Part Picker.

This Serve The Home article says that the board supports 32GB ECC DDR4 2666 DIMMs, but PCPP is saying there's a ton of issues with the ram and the CPU. I want to confirm that the parts in my list will work together before I order them and I'm so far unable to find concrete information on what should work.
https://www.servethehome.com/asrock-rack-x470d4u-review-amd-ryzen-meet-server/

Here's my parts list, and below are the compatibility errors it shows:
https://pcpartpicker.com/list/PFbs9r
>Problem: 128 GB RAM exceeds the motherboard maximum of 64 GB.
>Problem: AMD Ryzen 9 3900X 3.8 GHz 12-Core Processor and Crucial CT32G4RFD4266 32 GB (1 x 32 GB) Registered DDR4-2666 CL19 Memory are not compatible.
>Problem: ASRock X470D4U Micro ATX AM4 Motherboard and Crucial CT32G4RFD4266 32 GB (1 x 32 GB) Registered DDR4-2666 CL19 Memory are not compatible.

Ryzen CPUs only support UNBUFFERED DIMMs.
However, PC PartPicker is wrong about 64GB limit. The board should run fine with 128GB (4x 32GB DIMMs).

I can't think of a better time to buy DDR4 ECC Unbuffered DIMMs, because they're cheap & easy to buy!

Here are some options:

https://www.kingston.com/en/memory/server-premier/ddr4-3200mts-ecc-unbuffered-dimm

https://www.crucial.com/catalog/memory/micron-did-agnostic
(Filter for "DDR4-3200" "ECC UDIMM" "VLP ECC UDIMM")

Then you can search the part numbers, or just go through "where to buy" links.
Sometimes Kingston will sell them directly. Looks like Micron will sell directly, also. Otherwise, you can order them from places like CDW. Compare prices, regardless.

Note if you install 4 Single-Rank DIMMs, they will run at 2933MT/s.
If you install 4 Dual-Rank DIMMs, they will run at 2667MT/s.
No need to buy slower DIMMs. Just buy 3200MT/s UNBUFFERED DIMMs, and the CPU/Board will do the right thing.

For example, I have a X470D4U and when I went from 2-sticks to 4-sticks of KSM32ES8/16ME (16GB Single-Rank), it auto-downclocked from 3200MT/s to 2933MT/s. My CPU is R3-3300X, so same IOD as 3900X. Note I'm using the latest Beta BIOS (4.26 Beta, AGESA 1.2.0.7).

I figure the same ram compatibility will go for the X570D4U as well, since it just has a different chipset