MBT -> GPT to reuse existing installation

Good morning.
I had a working system using a old linuxcnc version (+- 5 years old). It was running fine, but the motherboard needs to be replaced.
I was unable to boot the same SSD on the new motherboard, so I suppose that from what I have read that the issue is more likely because the current installation was done on the old MBR.
The new candidate motherboard only has UEFI so for what I have read, I must convert the current disk to use GPT.

I have read some online information, and there are many steps involved on the conversion. Should I try to start from a new installation or still the conversion would be less trouble. What is your opinion?

Disable "secure boot" in BIOS.
Also enable "legacy" or CSM or both.
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Changing from MBT (should be MBR or Master Boot Record) to GPT will destroy any info on the drive, so to do that would require cloning the partition (not the drive) to another drive, switching partitioning and then cloning back that partition. Either way you look at it, very dangerous and not much chances of working properly.
And more importantly, that is not the reason for failing to boot.

Thank you for the reply.
I did what you suggested, before my post, and the motherboard does not recognize the SSD. Strangely it displays a very fast message that I was able to see:

There is no vBIOS support detected in this card.
'BIOS CSM/UEFI Mode' settings in BIOS will be changed to 'UEFI'

and automatically it moves to the BIOS screen, and the previous changed settings are converted to UEFI again.
Note that I do not have a separated graphics card.

Press F11 or F12 or on some PC's F8 after power on, see if you can select that SSD to boot from and also notice if there is more than one entry for it, usually the name of the SSD as one entry and another with UEFI SDD, try both.
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Edit:
Is it an ACER?
those require setting a BIOS password to be able to disable secure boot.

The issue is that the disk is not listed there.
Motherboard is MSI. I will try something else later today, but does not look promising.

Use a new SSD.
Bookworm is pretty good with UEFI but I think I would try installing Trixie to get any later enhancements now there is a beta ISO release
You should be able to install Linuxcnc with: The dev package installs halcompile etc