Hi guys,I bought my daughter a used SM-T820 and was unhappy with the performance with the latest firmware so I embarked on a 6-hour journey to get this debloated ROM to work. Through many trials and tribulations, I finally got it all done and working so I thought I would come back here and save the next person some pain. Here are the steps I followed to install this ROM, paying specific attention to steps 13A/B and 19A/B:
* NOTE: Formatting Data WILL wipe everything [including the internal storage]. So remember to make proper backups!
(1.) Enter Download Mode (Hold Power+Vol.Down+Home)
(2.) Flash BL, AP and CSC from stock ROM of choice with Odin v3.14.1_PatcheD
(3.) Go through startup configuration, skip everything
(4.) Turn on WiFi and connect, then go to System Update and click "Download and Install". You may need to do this multiple times if it fails, eventually it will succeed. Don't update or anything, just go back to settings.
(5.) Set time from automatic to manual then set date back more than 7 days prior.
(6.) Activate Developer Mode. Developer options should show OEM Unlocking option. Be sure to confirm it is showing and allowed.
(7.) Turn on USB debugging, allow PC to connect, accept the connection (check always allow)
(8.) Put tablet into Download Mode again
(9.) Flash TWRP with Odin (AP slot) but make sure Auto-Reboot is unchecked.
(10.) Restart with Power+Vol.Down+Home but quickly switch to Power+Vol.Up+Home to go right into TWRP
(11.) Allow Modifications
(12.) Click Wipe -> Format Data, type yes and let it complete
(13A.) Install Magisk and then oreo encryption disabler (for Oreo)
(13B.) Install Magisk, then RMM V3 bypass and then Dmverity & Encryption Patch (for Pie and newer)
(14.) Restart system and let it boot (may take a while)
(15.) Skip through all the startup stuff, set time to manual and set back a month or more
(16.) Turn on WiFi and connect, then go to System Update and click "Download and Install". You may need to do this multiple times if it fails. Eventually it will succeed.
(17.) Developer options should again show OEM Unlocking option. Confirm then turn on USB Debugging and allow connection.
(18.) Reboot into TWRP and Format Data again
(19A.) Install the ROM (Magisk is already included, no need to install again) then oreo encryption disabler (for Oreo)
(19B.) Install the ROM (Magisk is already included, no need to install again), then RMM V3 bypass and then Dmverity & Encryption Patch (for Pie and newer)
(20.) Wipe Dalvik and cache then reboot, no need to confirm OEM unlocking or turn on developer apps again (unless you want them)
Very helpful thread, though some steps were confusing: https://forum.xda-developers.com/t/newbie-friendly-twrp-and-root-for-samsung-s3-tablet.3885114/
Best Samsung firmware site, no slow download b.s.: https://samfw.com/firmware/SM-T820/
12/23/2020 - Original Version
1/25/2021 - Update with corrections from forum feedback
Thanks to @NullCode, @BenG7 and of course @rorymc928 for creating the ROM!
where can I find RMM V3 bypass and then Dmverity & Encryption Patch (for Pie and newer? Many thanks!