It's pretty amazing how much raw computing power you can cram into a little space these days. If you are looking to go the route of a small form factor PC, a solid starting point is ASRock's B550M Steel Legend. It's a micro ATX motherboard with plenty of bells and whistles, including support for AMD's latest generation CPUs—and it's on sale at Newegg.
The vendor has it marked down from $154.99 to $129.99, which is already the cheapest around. However, there's also a $20 mail-in-rebate available that brings the cost down to just $109.99, once you jump through the rebate hoop and receive a check from ASRock.
This motherboard is based on AMD's B550 chipset, which itself is supposed to be an affordable alternative to X570. And for the most part it is, though there are some B550 motherboards that run a few hundred bucks, at which point you might as well hop over to X570.
The B550M Steel Legend is a bit higher end than the cheapest B550 motherboards. It is built for overclocking, part of which entails a 10-phase power design for added stability. ASRock also uses higher end components throughout, like premium chokes and capacitors.
Other amenities include a reinforced PCIe x16 slot, a 2.5G LAN port (something you don't always find on cheaper motherboards), two M.2 slots (one of which supports PCIe 4.0 SSDs), half a dozen SATA 6Gbps ports, and USB 3.2 Gen 2 connectivity.
Also be sure to check out our roundup of the best motherboards for gaming, for options on a variety of chipsets for AMD and Intel.