Installing a custom ROM on the Vivo 1801 (Vivo Y71) is notoriously difficult due to Vivo's strict security policies that typically prevent bootloader unlocking . While the hardware is based on the Qualcomm Snapdragon 425
Conclusion
If you are looking to refresh the look and feel of your Vivo 1801 without the risks of custom ROMs, consider these safer alternatives: vivo 1801 custom rom
Once the bootloader is breached, the next requirement is a custom recovery. For the vivo 1801, TWRP (Team Win Recovery Project) is the gold standard. Installing a custom ROM on the Vivo 1801