I believe you have already found out the information.
The download is a drop down menu at the bottom of the page.
Ryzen Pro CPUs are not supported in ryzen master I believe.
I am pretty sure i looked at the exact blog post in the past and it was not there, I think it has been added recently.
I was able to read and write to my X300 with the modified flashrom build posted over in "AGESA FW stack patched bioses for 3rd gen" at overclock.net, I just use freedos in the...
jzelectronic has the X300 L1.46 bios listed in their blog "31.12.20 19:13 BIOSe für ASRock Serie AM4". L1.46 has PBO, XFR, CPB, TSME, Global C-State. AGESA ComboAM4v2PI 184.108.40.206 SMU 220.127.116.11
I know this is the A300 thread, can't see a X300 thread like this one.
I got the X300, 3400G...
You should check out the X300 L1.46 bios listed over in the JZelectronic blog "31.12.20 19:13 BIOSe für ASRock Serie AM4", the drop down menu at the bottom of the page should have "DeskMini X300 - Version 1.46 (AGESA V2 1002)"
Bios is from an unofficial source, use at own risk.
It has PBO...