TWRP installation error Samsung S8

I am trying to install TWRP on Samsung S8

Heimdall v1.4.2

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Initialising connection...
Detecting device...
Claiming interface...
Setting up interface...

Initialising protocol...
Protocol initialisation successful.

Beginning session...

Some devices may take up to 2 minutes to respond.
Please be patient!

Session begun.

Downloading device's PIT file...
PIT file download successful.

Uploading RECOVERY
RECOVERY upload successful

Ending session...
ERROR: Failed to receive session end confirmation!
Releasing device interface...

On a smartphone
*Only official released binaries are allowed to be flashed*

How to fix?

Regain your privacy! Adopt /e/ the unGoogled mobile OS and online servicesphone


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welcome to this forum

this is due to a samsung protect feature, well known by @aibd ( Know your hardware - Samsung )
please share a photo of your phone’s download mode screen

The links to the material you gave refer to the 10 series of devices.
What about S8?

As predicted by @piero your phone is showing Prenormal. This is a conditional lock. Perhaps the solutions for S10 devices jumped out at you because they are more recent additions.

You might have use your skill and judgement to see if you can see which of the mentioned locks could have been applied by Samsung in your case.

This Search results for 'prenormal order:latest' - /e/ community would link you to others who have faced or are facing the same issue.

I followed all the steps in the instructions, did not help.
What else to try?

You are correct that Prenormal is not covered in the instructions.

You have a locked bootloader. Anything I could add will be repetition. Please ask again referring to the research you already made.

Here is a way, i think…