Legacy BIOS Bootloader on old HO Z800

Hello guys, it's my first post here, as I thought turning to a reddit community after having spent several evenings (with AI) to achieve my goals without success

I use an old HP Z800 workstation which still is a decent PC to me for what I'm doing. Along his years of service I often had fun installing different OS, since it had several ssd bays, even did a hackintosh once.

I recently decided to get serious with Linux, especially Linux mint but also still having fun while "hacking" this machine as much as possible, and thought also using my SSD NVMe (which we're connected on PCI-Express until now as "normal" fast drives) as boot drives.

I read this was possible with Clover or rEFInd bootloaders for old machines with BIOS, to detect the NVMe connected to the PCI-E port owing to a specific driver.

So here my 2 questions:

• is there somewhere on the internet an .iso containing CLOVER or rEFInd in Legacy BIOS version ? I went through all the versions on GitHub but I think there's only UEFI versions nowadays. My old Z800 has the latest BIOS version but is still unable to boot a drive on PCI-E.

-Since I didn't find this BIOS LEGACY version, I started to create a bootable usb on my own with the help of AI (Le Chat free) I managed to boot on it, start SYSLINUX which starts himself Clover, but the Clover menu stays empty (doesn't even detect my windows 10 drive which is normally connected on SATA). I tried different config.plist, even trying to give manually the path to the specific bootloaders on the drives but to no avail. I also tried this for the NVMe with a specific PCI-E driver for Clover, but the list stays desperately empty. The AI is slowly turning in loop now, telling me to redo the usb or try rEFInd (I did it but didn't come so far)

Do I miss something or has someone an idea to test further?