dual boot – I can’t choose primary or logical partition on Kubuntu

So I’ve been trying to install Kubuntu, my computer is a bit weird. My BIOS is UEFI apparently (it shows “Press F1 to Enter UEFI BIOS”) but my Windows is on Legacy and MBR, now this wouldn’t matter but I just can’t install Kubuntu.
The first thing I did was prepare a 120GB unallocated space for Kubuntu, then I ran the Kubuntu installation, things were going smooth, I created the 4 partitions it asked for (root, home, swap and efi) until I got to the final part, in which it gave me a Fatal Error, where it said something along the lines “Failed to execute install GRUB on dev/sda/ THIS IS A FATAL ERROR” and then I got kicked out of the installation with the bug reports and yeah.

This happened some time ago when trying to install Mint, and what I did to fix it was set some partitions (iirc it was just the root partition) as primary, and it worked fine. But on Kubuntu I just can’t find a way to choose “primary” or “logical” partition type! On the installation partition setup I can only choose the size, the beginning or end of the thing, the filesystem and the mount point! Please help, I just need to know how to do this on Kubuntu and it will much probably fix my issue.
Also, I tried installing the bootloader at dev/sda8 for the first time (sda8 was the efi partition), but that was just the first time and I got the error, then I tried again, this time on dev/sda/ which is the default (and I think it’s also the most correct one) and it gave me the same thing. I doubt this is related though

EDIT: It did make my system unusable after the error, I tried to restart and GRUB rescue couldn’t find a system or something like that. So after some time I just used Boot Repair on Kubuntu Live USB and I’m now using Windows, waiting for an answer so that I can install Kubuntu. And I didn’t get the option to “Install alongside Windows 10”, I only got some GUIDED options and the Manual one, which was what I used