“… use drives that you’ve preformatted with the GPT file format for UEFI mode, or the MBR file format for BIOS mode. …” i would say that the MS Windows on your device /dev/nvme0n1 will only boot in MBR-mode.
GRUB cannot handle a mix of UEFI- and MBR-mode.
If you have installed OSs in different boot modes you need to switch your UEFI to the corresponding boot mode before you can start an OS.
But how can i change that without to reinstall? Or get issue when i boot?
Maybe UEFI boot have be better than a few year ago, but i know its lot of issue of it.
There reason many dissable it.
How works security boot? because i got menu item for that, but its only reboot computer.
So i guess its not added\support for it?
I’m not familiar with MS Windows at all so i can’t help you moving your MS Windows from MBR boot to UEFI boot. Probably you can get some advice on that at a Windows forum.
What issues (beside switching boot mode in UEFI)?
Since 2016 i only use systems which boot in UEFI-mode and so far i never had any problems.
Without any knowledge on what operating system (name, release, …) you installed next to MS Windows it is hard to give you proper advice on this.
It is not only Windows that you have to reinstall with secure boot, but you also have to scratch the HDD and redo Open suse after. If you delete Windows partitions and reinstall it on the remaning parttion, you’ll get boot issues after. Tumbleweed will boot slowly and you’ll get side effects.
Same ball game if you convert MBR to GPT in Windows, but you are dual boot. You have to tweak Grub from Windows to add it in the boot menu. You also have to reinstall Grub in Yast after. In all cases you will have undesirable side effects.
Windows must be installed first and then you create a dedicated partition for Tumbleweed after. Both ISO’s must be made with the help of Rufus 3.5 in GPT only.