Not sure if you resolved the issue but I ran into the same issue last night after upgrading from v3.2 to v3.4/v4.90. Stumbled upon your thread to confirm I wasn’t the only one with this issue thought I am using windows instead of linux. But I was also using virtualization for linux… though window vm was having the same performance issue.
created 3 threads in reddit but didn’t get an answer.
Finally ran into this http://forum.asrock.com/forum_posts.asp?TID=8141&title=asrock-ab350-pro4-470-attempted-write-to-readonly saying to revert back to a previous firmware everything is working now as expected. see : https://i.imgur.com/Q7KiQOH.png I couldn’t even get to the installer before
You must flash to bridge 3.4 and then to a stable firmware… for me that was v3.2… I don’t trust v3.3
I hope this helps.
I’m running windows 10 pro 1803
System details: Graphics Chipset - Radeon ™ RX 480 Graphics Windows Version - Windows 10 (64 bit) System Memory - 16 GB CPU Type - AMD Ryzen 5 1600 Six-Core Processor