asus prime b460m-a

Hello, I have just bought a new mobo for PC which is ASUS PRIME B460M-A R2.0. Mobo recognizes my old disk: Samsung SSD 850 EVO but doesn't find it as bootable media... I've googled a bit and I have seen that I should maybe enable CSM mode but it's greyed out and disabled on this specific bios...

Hi there, I'm making this post on behalf of a friend I just spent most of the day trying to troubleshoot this problem with. He has no PC able to make this post and I feel responsible more or less so I'll help fix it. Here's the specs and the issue: Specifications GPU: RTX 2060 CPU: Intel...