dual boot - Grub issue after installing new distro

I had LinuxMint + Windows 10 in dual boot, everything was working fine.

For some reason, I installed Kubuntu instead of LinuxMint, everything went smoothly. When starting my laptop for the last weeks, the grub let me choose between Ubuntu and Windows.

I'm used to start automatically Ubuntu OS, and it worked fine. But I recently tried to start windows OS, and it wasn't working anymore : it comes back to grub when I select the windows boot.

So I started a live-ubuntu session, installed and run boot repair, you can find 1st Log here
http://paste.ubuntu.com/25591401/

I tried to run Recomended repair, and I get this message
"GPT detected. Please create a BIOS-Boot partition (>1MB, unformatted filesystem, bios_grub flag). This can be performed via tools such as Gparted. Then try again."

I did what I was told to do, (creating a Bios-Boot partition unformatted bios_grub flag with gparted) then I tried again to run Boot repair and the option Recommended repair, I followed instructions and it finished with an error message and this 2nd log :
http://paste.ubuntu.com/25591550/

I reboot my laptop (without usb live) : the Grub does not start but (tadam!!!) it is Windows 10 wich is starting automatically. I cannot have a booting choice anymore.

I would like to get (back) my working Grub when I start my computer. Anybody has an idea?

Thanks for helping. Tell me if you need more info.

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Thank you very much Rod for your help and concern.

I follow your instructions, and from How to change ubuntu install from legacy to uefi , I used the method 1. At the end (when it gives the pasteubuntu link for the logfile which is http://paste.ubuntu.com/25594817/ ), and it was written "an error occured".

When the laptop is booting, I can see very quickly (only appears a sec) something like "Failed to open EFI/grub... not found" and "Fail to load image...??"

What do I miss? It seems the new grub is not installing correctly?

PS : I wanted to try the method 2 with your refind utiliy. I copied it on a FAT32 (boot flaged) USB flash drive, but when I try to boot from it, no success. I probably miss something cause I'm really tired. I'll try smthg else and dig more of it tomorrow.

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I tried the second method (with refind) and I still have the same issue.
Booting from an usb with refind allow me to choose between .

• Boot Microsoft EFI boot from EFIPART


• Boot EFI/Boot/bkpbootx64.efi from EFIPART



• Boot EFI\ubuntu\grubx64.efi from EFIPART


• Boot EFI\refind\refind_x64.efi from EFIPART


• Boot Fallback boot loader from EFIPART


• Boot boot\vmlinuz-4.4.0.... signed from racine

I choose the last one and Kubunut started. then I install refind via line commands. I reboot the computer. I still have a quick message "Failed to load ...EFI...GRUB" appears at the beggining, then the laptop starts windows directly.

I suppose that I don't put the correct object (EFI booting shit) at the correct spot. I suppose also the sda9 I created is useless, but I'm not sure of it. I suppose I have toooooooo many options for starting my computer.