Download Stock Firmware ROM from the download link this
and flash with any SPD supported Flash tool like Spreadtrum
Download Lava Iris X19 Flash file
Install spd driver
1- Download the package & Extract flash tool.
2- Out of the icon appearing, Double click on UpgradeDownload.exe.
3- It will Launch the tool on PC.
4- Click on Load Packed button & Select the Firmware with extension .pac at end.
5- Click on Downloading button which is at third position.
6- Switch off your Mobile & connect it to PC using Volume down key.
7- It will lead you to Successful flashing.