[Samsung Galaxy Tab A series ROMs, Kernels, Recover] qntmcat:
I've gotten it maybe working after a few iterations. I'm not expert at this, so this is pure cargo-cult work of just trying to follow the various instruction sets out there, but I've tried several iterations and documented a few FAIL messages. Try not to laugh too hard at my flailing.

What I did:

1. Restored to OEM (ODIN 3.14.4, used theBL/AP/CP/CSC from XAR-T290XXU3BTI2-20201021133521.zip)

--Restore completed normally

2. Confirmed functional. Performed "Let's Go" setup. WiFi was working and detected my AP during setup. Did device registration etc.

--Tablet working normally

3. Stopped tablet, put back into download mode,used Odin3 again , AP = Nexus_Stock_AQ_T290XXU3BTI2-20201206.tar.md5 (no BL / CP / CSC selected)

--Fail at system.img.ext4

--Error on the tablet: SW REV CHECK FAIL : [system]Fused 3 > Binary 0

4. Restarted, and redid step 1 to restore back to stock.

--Did not confirm status, in case first boot did something to cause the issue

5. Restarted, and repeated step 3

--Same failure point / message

6. Restarted, redid step 1 again to restore

7. Restarted immediately and restored again, this time using stock BL / CP / CSC along with custom AP above.

--Same failure point / message

This next works, but there is an error, an

8. Reread information above, decided to apply the TWRP MTP correction you list above. I know this is stupid, because of version differences, but I thought it might be worth a try because I think this may have been what I did to get it partly working before. (Is there another TWRP MTP corrected image I would use here??)

9. Repeated step 1 to get fully stock

10. Restarted, Pushed the TWRP image from your post reference above in AP, along with the BL/CP/CSC files from BTI2 (because dumb? This seems like it shouldn't work because of the version difference.)

11. Pushed without issue. Made it to the TWRP menu. Did a wipe. Restarted.

12. Used Odin to push stock BL/CP/CSC files along with your custom AP again.

13. It worked (kinda.) I did not get the rev check fail I got before, but I did get an error when the vbmeta.img came up which read: SECURE CHECK FAIL : VBMETA -- But Odin kept pushing and gave me a PASS! at the end.

14. Restarted. Again, caught TWRP on the restart and told it to wipe again (just to be safe, but this could also have just been stupid)

15. Restarted.

16. Okay, this time I got to the "Start" button, and it actually made it to the wifi screen *and detected my AP!

17. Set up google account -- Initial login worked, but 2-step verification did not (brings up the correct prompts, but both the bluetooth and usb titankey get to a certain point and then halt. In the case of the bluetooth, it gets to the point where it says you need to enter the 6-digit code from the back of the key, but pressing NEXT button does nothing. In the case of the usb titankey, it prompts for the "tap the gold disc", I get lights on the titankey, but it never recognizes the tap.)

18. Used the "tap on a phone" method instead,, which worked.

19. Noticed an odd message after the "checking your account" message, couldn't catch all of it, but it said something about screen lock already being on. Probably benign.

20. Changed font sizes and swapped wallpapers just to check them out. Works as expected.

21. Tested Play Store. Loads. Was able to update apps (some are still updating) and install a few things I wanted. No issues.

22. Wanted to validate that the bluetooth titan key worked, so I went and paired it. Works fine from this level, got the "enter the code" prompt from paring,.

23. All apps I've tried so far have worked. Will explore some underpinnings to see if I find any other goofiness.

So, WiFi works now? Didn't work last times I did it a few days ago? Not sure what I did different, but pushing TWRP (even if it's the wrong version) seems to have done the trick.

(Now I just have to try to parse out whether I need to do the multidisabler / root / other stuff.)

I did find something not working, which is the screen lock. I am unable to get it to set to anything other than SWIPE. It *tries* to set it when I go to pin/password/pattern, it loads the change function for that thing, but when I complete the change, I get the same error I got during setup:

Screen lock was already changed. Try again with the new screen lock.

Additional: While bluetooth seems to be working for device connections and so on, I don't appear to be able to get sound output to actually go there, even when the paired device is listed as the correct one for sound output. Probably more of my just being wrong and uninformed.