Hey Benny!

yes legecy is supported, but uefi is default

Same situation here, however booting to nvme took a bit of head banging and rebooting to more or less get working with uefi. I am not 100% happy with it but all things considered I can learn to live with it. For the record here is what dmidecode thinks about the bios;

BIOS Information
Vendor: American Megatrends Inc.
Version: P1.30
Release Date: 11/27/2020
Address: 0xF0000
Runtime Size: 64 kB
ROM Size: 16384 kB
Characteristics:
PCI is supported
BIOS is upgradeable
BIOS shadowing is allowed
Boot from CD is supported
Selectable boot is supported
BIOS ROM is socketed
EDD is supported
5.25"/1.2 MB floppy services are supported (int 13h)
3.5"/720 kB floppy services are supported (int 13h)
3.5"/2.88 MB floppy services are supported (int 13h)
Print screen service is supported (int 5h)
8042 keyboard services are supported (int 9h)
Serial services are supported (int 14h)
Printer services are supported (int 17h)
ACPI is supported
USB legacy is supported
BIOS boot specification is supported
Targeted content distribution is supported
UEFI is supported
BIOS Revision: 5.16

The "BIOS boot specification is supported" appears to be flakey wrt nvme disks. Your mileage may vary.

Life is good,
Maurice

... Nearon nu cyningas ne caseras ne goldgiefan swylce iu wæron.
There are not now kings nor caesars nor gold-givers as there once were.
--- GNU bash, version 5.1.16(1)-release (x86_64-lilmikii-linux-gnu)
* Origin: Little Mikey's Brain - Ladysmith BC, Canada (1:153/7001)