These are ROMs taken from a similar device (often the Redmi 8 or another Snapdragon 439 device) and "ported" to the Vivo 1801 by modifying the system files.
Fast forward to today, and Funtouch OS feels clunky, heavy, and outdated. If you have this device gathering dust in a drawer, or if you’re still using it daily but struggling with lag and bloatware, there is hope. vivo 1801 custom rom