Follow up and hopefully a closing post.

Purchased a new motherboard, the exact same PN. Before I purchased the board, I made sure that the seller of the board had a good return policy, no restocking. For the moment the problem appears to be solved.

Thanks very much at @ubuysa, you had the right idea from the beginning.

Just an FYI, I did try safe mode with networking, but it appears that functionality has been completely removed. It cannot even be accessed from the lock screen anymore.

One last thing I found interesting. After trying the new motherboard for a week, I reinstalled the old one to transfer my Windows OEM license, and it no longer worked. Just a blinking power light, nothing else.

Was it on the edge of death and R&Ring it finally killed it? I don't know, but it's done for now.

Thanks again, @ubuysa!