You can only have 4 partitions with msdos tables, you must have gpt tables. You also have W10 using UEFI, in order to get Ubuntu to boot using UEFI it must have a Fat 32 EFI partition, that may be the /dev/sda1 but it isn’t marked for formatting. Here is a link to something like what you are attempting https://askubuntu.com/questions/726972/dual-boot-windows-10-and-linux-ubuntu-on-separate-hard-drives. I do not use UEFI and I believe the tutorial you used was for running linux and windows side by side. Good Luck. Can you still boot Windows?