[Galaxy Tab 4 Q&A, Help & Troubleshooting] jirido:
Hi. I have had problems with flashing twrp to recovery. The device I try to flash is a GALAXY TAB 4 t535 from 2014 with android 5.0.2 and a security patch from 2017-03-01. The kernel is 3.4.01023903, buildnr LRX22G T535XSS1BRH1.

I try to flash it from an arch linux with both adb/fastboot v1.0.41 and Version 31.0.3-android-tools

Also I have tried heimdall v1.4.2

"adb devices" finds the device as 10e0a213 but using fastboot with the device in download mode, ie trough "adb reboot-bootloader", fastboot can not find any device. I have made a rule so that my linux mount the device as "user", ie jirido but also tried both as root and with sudo.

lsusb tells me:

Bus 001 Device 031: ID 04e8:685d Samsung Electronics Co., Ltd GT-I9100 Phone [Galaxy S II] (Download mode)

ls -l /dev/bus/usb/001/031 tells me

crw-rw-rw-+ 1 jirido adbusers 189, 30 4 dec 15.05 /dev/bus/usb/001/031

Still no device shows up with fastboot.

When using heimdall I write to the device but it seam like it actually can't write the image down even thou the blue line shows up.

Here I flash the tar image but I have also tried with the .img image both with the recovery name and its original twrp-xxx name.

The results have been the same. No luck and stock recovery.

---------------------------------------------------------------------

$ heimdall flash --RECOVERY ./Downloads/recovery.tar --no-reboot

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

100%

ERROR: Failed to confirm end of file transfer sequence!

ERROR: RECOVERY upload failed!

Ending session...

Releasing device interface...

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I then reboot directly to the recovery.. and right as expected there is the stock recovery.

From this I draw the conclusion that recovery is still unwritable.

Following this conclusion I searched and found out that I should toggle the "OEM unlock" setting that can be found under "developer options". But when I looked, it wasn't there. After searching some more on dear internet I found information that told me about a bunch of tricks involving unsetting automatic time and update, setting time backwards a couple of weeks and updating manually and so on.. all in the hope of that the "oem unlock" switch should show up.

With the time set to the past, and no automatic updating I then try to update manually when the update function tells me that: The operating system on your device has been modified in an unauthorized way. Try downloading updates using smart switch on your pc or visit customer service center.

Thinking that this might be something in the tab's history I then factory reset the device with the OEM recovery but sadly it did not help at all and I still get the same splash about unauthorized modification when trying to do a manual update

That is where I am at now wishing to the goddess for good advice.