LineageOS is the grandfather of custom ROMs. It is the successor to the famous CyanogenMod.
Stock recovery won't flash custom ROMs. You need TWRP (Team Win Recovery Project). oppo a83 custom rom
Warning: unlocking bootloader, flashing custom recoveries, and installing custom ROMs can void warranty, erase data, or brick a device. Proceed only if you accept risk. Back up everything important before starting. LineageOS is the grandfather of custom ROMs
Refreshing Your Oppo A83: A Guide to Custom ROMs in 2026 If you are still rocking the flashing custom recoveries