[Samsung Galaxy Tab A series ROMs, Kernels, Recover] K9100ii:
You're welcome, and excellent.

The "A6" boot splashscreen you describe would actually be the completely stock and static splashscreen.

I don't think there should ever be any complete expectations for a build for the T585. As I've always said before in my previous posts, I'm only going to attempt to setup sources for the T585 to build for it, whenever I have the time to, which unfortunately I've still ended up not having much of. I can never be certain if I'm going to succeed.

While I do think I have a decent enough chance at success (although I'm less confident than I was before after taking a better look at the previous sources that were used for the T585), the undeniable reality is that there can only possibly be full expectations for me to setup proper sources and get working builds if I have physical access to a T585, to freely test and "experiment" on. Builds for the T585 boot on the T580, just as builds for the T580 boot on the T585, so I can take advantage of that, however, it's a far from perfect compromise, because that can only be used for testing of fairly basic things.

With that being said, what I have now is a vendor tree that I've converted for the T585 several days ago and am not very sure about for now here: https://github.com/TALUAtGitHub/android_vendor_samsung_gtaxllte I've mostly used the blobs that were previously used for the T585 for a safe starting point, although I would prefer to have more up-to-date blobs, which is something to potentially consider later. Now, the next big thing would be to setup a device tree. There wouldn't be very much to add to, or replace in, my device tree for the T580, to convert it for the T585, after all, it's just mobile networking/telephony, GPS, and vibration, however, it's not all about simply adding and replacing stuff, but also most importantly, of course, having everything setup such that it actually works, and this is where things get somewhat difficult and I have to make hard decisions that I'm not entirely certain about. Also, there's the sepolicy, containing all of the SELinux rules, to which new rules would need to be added for the additional functionality, which would be a relatively involved process. I'm hoping for eventual success with all of this stuff.

Thanks for your report. Looking into this, I've found that the ramdisks for builds from my device trees for TWRP for the P580 and P585 are around 2MB larger than those for the T580 and T585, due to the inclusion of a few extra languages for the P580 and P585 that require some fonts that are quite large, and they end up being around 16MB. It seems that the bootloaders refuse to boot from recovery images with a ramdisk that is larger than 16MB.

I've made another TWRP build for the P580, with the ramdisk compressed using LZMA compression, rather than the standard gzip compression with which the ramdisk in the first build was compressed, bringing the size of the ramdisk from that size of around 16MB down to around 11MB, and therefore, that error from the bootloader about an invalid ramdisk length should no longer occur with it, and it should work. The image of it can be downloaded from here. Could you please test that build out?