Oldfred's answer is correct; however, I want to add a few points:
- As oldfred says, the BIOS Boot Partition (what GParted identifies by its
bios_grub flag) should not be an issue should you install another OS; however, two of your ext4fs partitions have the
msftdata flag, which identifies them as being of the Windows Basic Data Partition type. Thus, if you install another OS -- and especially if that OS is Windows -- you may run into problems because the other OS may try to interpret the filesystems as FAT or NTFS and, when that fails, may offer to "prepare" or "format" the partitions; and in this context, both those words mean "destroy." The solution is to remove the
msftdata flag in GParted or
parted; or if you use
gdisk, change the type code from 0700 to 8300.
- GPT is more often used with EFI-mode booting than with BIOS-mode booting. To boot in EFI mode, you need a computer that uses an Extensible Firmware Interface (EFI) firmware (or UEFI, which is EFI 2.x), an EFI System Partition (ESP), and an EFI boot loader for Linux..
- Windows tightly ties its partition table type to its boot mode -- it boots from MBR disks only in BIOS/CSM/legacy mode and from GPT disks only in EFI/UEFI mode. Thus, your use of GPT disks means that you'll be able to install Windows only in EFI mode. This won't even be possible if your computer is old enough to have a conventional BIOS, except by using a "software EFI" like DUET or Clover. If you have EFI firmware, you'll be able to install Windows, but then you'll have a mixed-mode configuration -- Windows in EFI mode and Ubuntu in BIOS mode. This is awkward to manage, and the best solution is to install an EFI boot loader for Linux. If you have a conventional BIOS, your best choice for dual-booting with Windows is likely to be to convert from GPT to MBR. My
gdisk program, which is installed by default in Ubuntu, can do this, with some caveats; see this page of the
gdisk documentation for details. Many non-Windows OSes, such as FreeBSD, are happy to boot from GPT disks in BIOS mode; but some older ones, such as DOS, can't handle the task at all, AFAIK.
Overall, the first issue (the incorrect
msftdata flag on two of your partitions) is worth fixing right now; although doing so is not critical for an Ubuntu-only installation, it will be a useful safeguard in case you boot a non-Linux emergency tool or if some obscure Linux utility run in Ubuntu makes bad assumptions based on the type code.
If you're happy booting the way you're booting, I wouldn't suggest installing an EFI boot loader at this point, much less converting from GPT to MBR; that would be fixing what ain't broke, as the saying goes. You should bear the linkage of partition table type to boot mode in mind if you decide to install another OS, though.