Always perform a read-back backup of your firmware before flashing new files. If you'd like, I can: Provide a list of specific drivers to download.
List of known OPPO/Realme preloader key combos (based on 2022–2023 models) oppo realme mtk preloader
Uncheck the Preloader partition if your device is currently turning on or boot-looping. Flashing an incompatible preloader can permanently hard-brick the device. Only check it if you are repairing a completely dead, hard-bricked phone. Always perform a read-back backup of your firmware