[Samsung Galaxy S10 Questions & Answers] JMailuhu:
Before you proceed, remember unlocking bootloader will delete everything from your device, and you probably won't be able to boot back into OS. Note: unlocking bootloader will trigger KNOX indefinitely so you won't be able to use SamSung proprietary apps like SamSung Pay and SamSung Vault, even if you revert back to stock firmware or did not flash a recovery/ROM.

Flashing Stock Firmware with ODIN (without bootloader unlock) does not trigger KNOX.

Snapdragon devices are NOT supported with custom ROMs.

You said S10 so i'm going to base my tutorial on the SM-G973F (beyond1lte). (If this is NOT your model, replace it (SamFW / TWRP links) with correct variant. You need to be on the latest Android 12 Stock firmware in order to flash other custom ROMs onto the device. If you are, somehow, on a lower version, please update to latest SamSung official supported Android 12 (OneUI 4.1) first!

Download these files before you unlock your bootloader. This so you can always get back to stock if anything happens in the process.

Stock Firmware: Official Samsung Stock (Select correct CSC for your Region. Since there's no Belgian CSC i suggest getting "PHN" which is from The Netherlands. You can also check System>Android Info>Baseband Version and see what CSC your device came with originally)

TWRP: Official TWTP

ODIN: Odin v3.14.4

Samsung USB Drivers: USB Drivers

ADB: Latest ADB

VBMETA: VBMETA.TAR

Unlock BOOTLOADER:

1). Make sure you have ticked "Unlock OEM" in Developer Settings. (Press 'Build Number' 5x in 'About Phone' to unlock Dev settings). Note: Back-up important data and files such as photos etc. that are not synced with your Google Account onto your PC or external SD-card or any other storage medium!!

2). Turn off your phone! Hold the Bixby Button+VOL-Down and insert your USB cable into the phone while it being connected to a PC. Note: You will need a PC-to-Phone usb connection in order to get to the menu, a connection with say; wall-socket will simply not work. If you don't have access to a PC, you cannot progress any further.

Follow instructions on the Bootloader menu. Your device will be reset and will reboot, most likely into download mode.

3). If you did not reboot into Download mode, perform the same button combination as above, but at the Bootloader menu, hold VOL-UP.

Flash Custom Recovery:

1). Start ODIN and if you have your USB drivers installed and are in Download mode, it will show you that you're connected to Port:xxx. Click Options tab and untick "Reboot after flash".

Now put the TWRP.tar into AP slot, and VBMETA into CP slot. Press Start to begin the flashing process. Note: The vbmeta.tar prevents you getting a vbmeta/twrp error when you unsucessfully try to boot into recovery.

2). Turn off your device. Boot your device while holding Bixby+VOL-UP+POWER button. Keep holding it until the TWRP logo appears.

3). Follow instructions on how to flash a ROM on their respective XDA thread(s). Note: that most, if not all, non OneUI based roms need a different recovery (adb) since TWRP won't work on those. You can find those adb-recoveries in said threads.

4). If in any case you need to go back to stock firmware, boot ODIN and follow instructions of your downloaded SamFW stock.zip

I recommend EvolutionX v8.4 (A14) ROM if you want a barebones stock Pixel rom with lots of customization and exellent battery life (I get 6.5h SOT, 25+h IDLE).

Ps. Als er wat is laat maar weten!