You have two choices:
- Install in EFI/UEFI mode -- The installer booted in this mode but refused to install because the disk was an MBR disk rather than the GPT disk that Windows requires for an EFI-mode installation. Thus, to install in EFI mode, you must convert the disk to GPT. Several third-party disk utilities, including my own GPT fdisk (
gdisk), can do this without damaging the partition you want to preserve. (Note, however, that no partitioning operation is 100% risk-free. Thus, I recommend making backups. I make that same recommendation because of the risks involved in installing a new OS, even without a partition table conversion.)
- Install in BIOS/CSM/legacy mode -- If you can get the installation medium to boot in BIOS mode, you can install to the disk in its current MBR configuration. The trick is to get the installer to boot in BIOS mode. The details of how to do this vary from one computer to another. As a general rule, you must enable an option in the firmware setup tool called "CSM support," "legacy boot support," or something similar. (The "legacy USB support" option you found is not the right option -- that option has to do with how USB keyboards and mice are treated, not to BIOS- vs. EFI-mode booting.) You may also need to select the installation medium via an option in the boot manager that names the device without the string "UEFI" appearing.
As a general rule, I recommend doing EFI-mode installations whenever possible. See this question and my answer to it, along with this web page of mine on the CSM, for details of why I recommend EFI-mode booting. In brief, EFI mode offers some modest advantages over BIOS mode, such as (usually) a slightly faster boot time and (on newer computers) Secure Boot. EFI is also the native boot mode; booting in BIOS mode basically requires running a BIOS emulator (the CSM) on the firmware, which complicates the boot path. OTOH, some early EFI implementations (from ~4 or more years ago, mostly) were flaky, and there is that modest risk involved with the MBR-to-GPT conversion. In some cases, these issues may outweigh EFI's advantages, which are far from overwhelming for most users.
EDIT:
The output you note (MBR: MBR only along with GPT: Present) indicates your partition table is in an inconsistent state -- the disk has what looks like a valid MBR, but there are also traces of GPT data. The usual cause is that the disk had been used with GPT, but at some point a GPT-unaware tool was used to create a fresh MBR partition table on it. If this is the case for you, you should pick the 1 - MBR option in rEFInd to have it convert the MBR data to GPT form. If you're uncertain, though, you can try to load the GPT data to see what it looks like, but do not save it back out with the w option -- at least, not unless you become convinced that the GPT data are more accurate than the MBR data.
