From this post you get a good BLU F91 Firmware Flash File official stock ROM tested 100% and approved perfectly from the source BLU F91 Flash File with flash tool, USB driver, and how to flash it
Blu bold spec
PROTECTION
Corning Gorilla Glass 5
6.8 FHD+ 20:0
Infinity Dot Curved Display
1080 X 2460
393ppi
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