S6 Lite - SM-P610 (gta4xlwifi) Cannot reboot into Recovery from Odin Mode

I love /e/ and use it as my main OS on my OP6T & SM-T713. I’m upgrading to a SM-P610, or trying to!

I have flashed many devices, including Samsung with /e/ & Lineage. I’m not generally a complete muppet. However, I’m following the installation doc (https://doc.e.foundation/devices/gta4xlwifi/install) which omits the unlocking process, up to ‘7. Manually reboot into recovery:’ which is impossible!

The firmware is as I bought it, P610XXU2DUL9 which appears to be the last Android 11 release, as stated in the requirements. I’m using the recommended heimdall binary on POP-OS. I’m installing recovery-e-1.0-r-20220526188878-dev-gta4xlwifi.img

During install I get:

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

And a message on screen complaining ‘Only official release binaries are allowed…’

I’m guessing those are normal.

Then comes the ‘impossible’ bit, reboot directly into the new recovery!

From Odin mode, I can reboot with power+Vol-down or power+both-vol
I cannot power off and can find nothing online on how to.
There doesn’t appear to be a way to do it via software either.
So, the moment the screen goes black, I switch to power+Vol-up (either releasing all buttons first or just moving from Vol-down to Vol-up whilst holding power. Either way, it just boots as normal. I’ve repeated this about 10 times without smashing my brand-new tablet into little pieces and jumping up and down on the pieces for good measure.

Clearly I’m missing something. Probably obvious. But I’ve exhausted all approaches I can think of.

Can you help me, please? Anyone, any ideas welcome. Many thanks.

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You are not the first one with this problem on very recent Samsung…

Search results for 'unlocking bootloader and flash vbmeta on s10' - /e/ community
Search results for '‘Only official release binaries are allowed...’' - /e/ community

You will find this tutorial : [RECOVERY][OFFICIAL][3.6.1-x] TWRP for Galaxy S10/e/+/5G Exynos | XDA Forums