Dear friends, I’m happy to tell you that our 3mdeb company (a prominent contributor to the world of opensource firmwares) - has successfully ported an opensource coreboot BIOS to MSI PRO Z690-A WiFi DDR4 motherboard! 
Although at the moment not everything is working (i.e. no sound yet) - we already got Ubuntu Linux booting and it’s just a matter of time before the remaining problems get fixed.
Opensource coreboot BIOS already supports quite a lot of devices - ranging from the laptops to workstations & servers - and I’m sure that there you can find a great board for your needs, considering your personal “freedom-security/performance” balance:
- either without the Intel ME / AMD PSP creepy “co-processors” and with a minimal amount of closed-source binary blobs (or none at all: such devices have been designated into the libreboot project) ,
- or with a few issues - i.e. with ME (could be me_cleaner’d in attempt to deactivate it) and some binary blobs - but a more modern & powerful hardware that’s still supported by coreboot (which delivers the security, quality, features and almost-lifetime firmware updates not available with the proprietary BIOSes).
However: usually by the time a coreboot port gets done for some particular board it’s already long gone from a market, and the fans of opensource secure firmwares have to search for the used devices. And even when a coreboot is generously provided by a board’s manufacturer “out-of-the-box”, such hardware usually goes for a premium price because of small-scale production and has a limited availability.
Behold a truly unique case, where - despite the technical hardships related to the “closeness” of modern x86 hardware - coreboot has been successfully ported to a popular mass-produced board that’s still widely available! 
P.S. If you’d like more info - here’s a Phoronix article and also a homepage of this motherboard’s coreboot port. + Make sure to subscribe to vPub newsletter to get notified about our next vPub online party - a great place for talking about the opensource firmwares & open hardwares and just having fun 
