Most NOR Flash brands should be supported in NCS, given the right configuration. The correct parameters for the QSPI flash hardware must be configured using the nordic,qspi-nor device tree node in either the board DTS or using a device tree overlay.
In addition make sure that CONFIG_NORDIC_QSPI_NOR_FLASH_LAYOUT_PAGE_SIZE matches the page size of the NOR flash that is used. You can see a demonstration of adding external flash in the Bootloader documentation.
