@RealTehreal
Step-by-step instructions, in case, someone else has the same issue:
1.: yum history list to get the transaction id of the last update.
2.: yum history info # with # being the id from step 1, to list the updates done in this transaction. The interesting part for me was
Updated microcode_ctl-2:2.1-26.xs26.2.xcpng8.2.x86_64
Update 2:2.1-26.xs28.1.xcpng8.2.x86_64
3.:yum downgrade microcode_ctl-2:2.1-26.xs26.2.xcpng8.2.x86_64 to downgrade to the previous version. You will have to enter the older version for this command.
4.: Wait until it's done, reboot, test, pray it'll work again.
This is just a workaround! Microcode updates are important security and/or functional updates. Downgrading can lead to security issues.