Yes, the information that you provided is useful. It is consistent with my earlier guess, that grub (via BIOS) is not able to read your 4T disk.
Apart from that, it looks as if your installed system is intact.
Here’s a bit of my analysis.
Your first grub screen shows: cmdpath=(hd1,gpt1)/EFI/opensuse
That’s good. I get something similar on my local tests.
Your second grub screen shows: prefix=(hd1,gpt1)/boot/grub2
That’s bad. It should show: prefix=(lvm/system-root)/boot/grub2
So it has processed the line setting prefix. But it failed to find your root volume in the LVM.
So what can you do about it?
Suggestion 1: You could copy parts of “/boot” into the EFI partition, and boot your system that way. But it will be awkward and high maintenance, because you will have to repeat that copying after every kernel update.
Suggestion 2: Do a reinstall without the LVM.
In the reinstall, again go with the guided setup.
On the first screen of the guided setup, check the boxes to allow it to delete linux partitions and maybe other partitions as needed. Note that you can abort without changing anything if you don’t like the proposal.
On the next screen, choose encryption but do not choose an LVM setup.
On the next screen, select the option for a separate “/home”. And this one is important (I’ll explain why, a little later)
I just tested doing this, though I aborted before doing any actual install.
In my test, it setup a root partition, a home partition and a swap partition with all of then encrypted. Since it only asked once for an encryption key, I presume it used the same key for all.
What you will want to check, is that it puts all of these on your same disk (the 4T disk). If it does something you don’t like, you can abort the install and try again using the expert partitioner. But that is a bit harder to explain, so first see if this works.
Doing it this way, the root partition should be toward the start of the disk. You want it to be within the first 2T. The reason for a separate “/home” is related to this. If you do not use a separate “/home” then the installer will setup a huge root partition which will be most of the 4T in space, and you will have the same problem as with the LVM setup. With a separate “/home” that should not happen. Maybe grub won’t be able to read the home partition, but it doesn’t need to actually read that. You will probably end up with partition 2 as root, partition 3 as “/home” and partition 4 as swap.