Disable Legacy USB support and cannot change back

The board is Z590-C/ac, using L1.93 Beta BIOS, and I have an IBM model M PS/2 keyboard I'd like to use, but as long at it is connected to the on board PS/2 port, booting will always comes to UEFI setup screen unless I keep smashing F2. And this keyboard does not work inside UEFI setup, although the caplock/numlock light can lit up and be changed by hitting corresponding keys. After entering Windows 11, this keyboard can be used normally, are there any thing special about much older PS/2 keyboards that they are not properly supported by the UEFI utility?

Then I tried to change setting in UEFI setup and disabled Legacy USB Support and reboots, unfortunately, this time, my normal USB keyboard and mouse connected to the USB 2.0 port no longer powers during UEFI, and the PS/2 keyboard still not doing anything in UEFI screen.

Then I tried a combination of CMOS battery or trip CMOS reset pin, disconnecting from power cord. It seems something might has been reset, as the "CMOS defaults has been loaded" screen has pop up, but the USB keyboard is still not working at boot screen, so I cannot bypass this screen unless I connect my model M PS/2 keyboard to F1 continue and still neither USB keyboard nor "abnormal" PS/2 keyboard work in UEFI config utility. But once I managed get to Windows 11 they both work fine. I also noticed the UEFI screen is still the advanced mode, no the easy mode, so the load UEFI default via remove battery does not restore everything. However, reset CMOS still changes the Intel RST controller thus the RAID no longer works so I cannot access some of my files.

Thus basically I failed any attempt to reset this option, it seems my only hope is on Monday a "modern" PS/2 mouse and a Y split cable will arrive and hopefully I can get out of this situation.