Vivo typically blocks bootloader unlocking on budget models like the Y1s to maintain system security. Without an unlocked bootloader, you cannot install a custom recovery (like TWRP) or a custom ROM.
Attempting to force a custom ROM onto a Vivo Y1s comes with significant risks: vivo y1s custom rom
Most developers have not released dedicated custom ROMs for the Vivo Y1s (model PD2014F) due to the restricted nature of Vivo’s Funtouch OS and the MediaTek MT6765/MT6771 chipset. Vivo typically blocks bootloader unlocking on budget models
If you manage to unlock the bootloader using unofficial third-party tools (like UnlockTool ), you might be able to flash a GSI ROM since the device supports Project Treble. vivo y1s custom rom