The A300 and X300 chipsets, which also target SFF systems, have been around for a while, but not many vendors have taken advantage of them. The ASRock DeskMini A300 (opens in new tab) is one of the handful systems that actually features an A300-based motherboard. It'll be interesting to see whether the Pro 500 chipset gains more favor from AMD's partners. Like the A300 and X300 chipsets, the Pro 500 chipset also lives on the existing AM4 platform.
According to AMD's website, the Pro 500, as well as A300, are "geared toward practical consumer and commercial users who need a simple, small solution." Meanwhile, the X300 chipset targets enthusiasts and overclockers.
In terms of similarities, the A300 and X300 chipsets support four USB 3.1 Gen 1 ports, two SATA ports, two M.2 ports and RAID 0 and 1 arrays. However, the A300 chipset only supports one PCIe 3.0 slot and doesn't allow for overclocking. The X300 chipset is a bit more generous in terms of features as it enables up to two PCIe 3.0 slots and overclocking. The PCIe 3.0 slots on both chipset operate at x8 with A-series and Athlon chips and at x16 with Ryzen chips.
Unfortunately, information on the Pro 500 chipset is pretty scarce. If we had to make a guess, we suspect the Pro 500 chipset is based on a similar design as AMD's high-end X570 chipset.
Additionally, Lenovo's IdeaCentre T540 (opens in new tab) and ThinkCentre M75s (opens in new tab) desktop PCs are listed as employing motherboards that are based on the AMD Pro 560 chipset.
It's uncertain if the Pro 560 is the same as Pro 500 AMD listed on it's website. However, the specifications for Lenovo's systems point to the usage of PCIe 3.0, so it appears that the Pro 560 chipset doesn't support the latest PCIe 4.0 standard.