I meant to include the link to the firmwares page.
Guides exist for flashing the Vim. If it is your first ARM device flash, read carefully before flashing. Multiple methods exist. It is not difficult, but the more you know the less risk is involved.
See Khadas Documents page, under the Bootcamp tab, for guides.
If you have questions, the community will assist.
Linux runs pretty good from SD(fast card or flash drive), of course, it won't be as fast as NAND.