It was hard for me and it took me a long time to install and make Qubes work on my notebook, as you can see in this post, (one of the reasons being my hardware is old):
and the conversation continued with many more questions from me here:
I don’t really remember why I installed it in legacy mode, as you have more knowledge than me about Qubes, maybe you can deduct it from those messages?. Do you think it may also work in UEFI mode for my hardware? Do I need to reinstall both operative systems for that?
I remember I had a smaller SSD and then I upgraded to a bigger one, so I am not 100% sure if all that long process was done with the actual SSD as well. I don’t remember using any disk’s cloning software so I probably installed Qubes again in the new SSD.