New install, dual boot with windows 10, but windows is not in boot option

Hi
Here is an example on a spare ssd, note it’s sdb in your case it would be sda.


gdisk -l /dev/sdb

GPT fdisk (gdisk) version 1.0.1

Partition table scan:
  MBR: MBR only
  BSD: not present
  APM: not present
  GPT: not present


***************************************************************
Found invalid GPT and valid MBR; converting MBR to GPT format
in memory. 
***************************************************************

Disk /dev/sdb: 488397168 sectors, 232.9 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 3B79FEAE-53E3-4528-BB74-8A1238D5A6D1
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 488397134
Partitions will be aligned on 2048-sector boundaries
Total free space is 488397101 sectors (232.9 GiB)

Number  Start (sector)    End (sector)  Size       Code  Name

gdisk /dev/sdb

GPT fdisk (gdisk) version 1.0.1

Partition table scan:
  MBR: MBR only
  BSD: not present
  APM: not present
  GPT: not present


***************************************************************
Found invalid GPT and valid MBR; converting MBR to GPT format
in memory. THIS OPERATION IS POTENTIALLY DESTRUCTIVE! Exit by
typing 'q' if you don't want to convert your MBR partitions
to GPT format!
***************************************************************


Command (? for help): x

Expert command (? for help): z
About to wipe out GPT on /dev/sdb. Proceed? (Y/N): y
GPT data structures destroyed! You may now partition the disk using fdisk or
other utilities.
Blank out MBR? (Y/N): y

gdisk /dev/sdb

GPT fdisk (gdisk) version 1.0.1

Partition table scan:
  MBR: not present
  BSD: not present
  APM: not present
  GPT: not present

Creating new GPT entries.

Command (? for help): n
Partition number (1-128, default 1): 
First sector (34-488397134, default = 2048) or {+-}size{KMGTP}: 
Last sector (2048-488397134, default = 488397134) or {+-}size{KMGTP}: +260M
Current type is 'Linux filesystem'
Hex code or GUID (L to show codes, Enter = 8300): ef00
Changed type of partition to 'EFI System'

Command (? for help): n
Partition number (2-128, default 2): 
First sector (34-488397134, default = 534528) or {+-}size{KMGTP}: 
Last sector (534528-488397134, default = 488397134) or {+-}size{KMGTP}: +60G
Current type is 'Linux filesystem'
Hex code or GUID (L to show codes, Enter = 8300): 
Changed type of partition to 'Linux filesystem'

Command (? for help): n   
Partition number (3-128, default 3): 
First sector (34-488397134, default = 126363648) or {+-}size{KMGTP}: 
Last sector (126363648-488397134, default = 488397134) or {+-}size{KMGTP}: +171G
Current type is 'Linux filesystem'
Hex code or GUID (L to show codes, Enter = 8300): 
Changed type of partition to 'Linux filesystem'

Command (? for help): n
Partition number (4-128, default 4): 
First sector (34-488397134, default = 484976640) or {+-}size{KMGTP}: 
Last sector (484976640-488397134, default = 488397134) or {+-}size{KMGTP}: 
Current type is 'Linux filesystem'
Hex code or GUID (L to show codes, Enter = 8300): 8200
Changed type of partition to 'Linux swap'

Command (? for help): w

Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
PARTITIONS!!

Do you want to proceed? (Y/N): y
OK; writing new GUID partition table (GPT) to /dev/sdb.
The operation has completed successfully.

lsblk /dev/sdb
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sdb      8:16   1 232.9G  0 disk 
├─sdb1   8:17   1   260M  0 part 
├─sdb2   8:18   1    60G  0 part 
├─sdb3   8:19   1   171G  0 part 
└─sdb4   8:20   1   1.6G  0 part 

parted -l /dev/sdb

Model: ATA WDC WDS250G2B0A (scsi)
Disk /dev/sdb: 250GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start   End     Size    File system  Name              Flags
 1      1049kB  274MB   273MB   fat16        EFI System        boot, esp
 2      274MB   64.7GB  64.4GB               Linux filesystem
 3      64.7GB  248GB   184GB                Linux filesystem
 4      248GB   250GB   1751MB               Linux swap        swap

At the partitioning stage select expert and use existing partitions, not proposed ones and configure as required…