I actually decided to replace all three of my rigs mainboards.
ASRock Fatal1ty X370 Professional Gaming AM4 AMD Promontory X370 SATA 6Gb/s ATX AMD Motherboard
www.newegg.com
These are ATX, which I prefer, and they have the
proper slot-spacing for dual GPUs (triple GPU even, if you use a case with 8 expansion slots... of which I saw a recent Rosewill case for $55 that had 8).
PLUS! It has 1GbE (Intel, I think), wireless AC + BT, AND... 5GbE, using the Aquantia chipset.
So, in that respect, for $139.99 ($10 off), I get:
1) and older, but high-end chipset
2) support for Zen2 (might have to flash BIOS first with 1st-gen Zen)
3) No BIOS flashback button, but a clear CMOS button instead,
4) Support for dual/triple GPUs.
5) And the piece de resistance,
5GbE. (Which should step down to 2.5 or 1Gbe if need be.) PLUS 1Gbe as well.
Given my personal desire for 4 and 5, I think that I made a fairly wise choice... other than basically no Zen3 support. (Edit: And of course, no PCI-E 4.0 support either.)
Edit: 2020-08-20: I got my 3x boards. BNIB. Interestingly, they DO say "Ryzen 3000 Desktop Ready", so I presume that these are relatively new stock, and flashed with the newest (or new enough) BIOS to take my Ryzen R5 3600 CPUs.