Update 10/11/25
I've since done more research, and I believe I can definitively say which consoles can run what dashboards.
2.0.1888-2.0.2857: MOSTLY WORKS (on Y1 consoles), DOES NOT BOOT. I could be wrong about 2857 on Rheas, but all of these dashboards require a Y1 GPU, otherwise the console will throw an E78. From what I hear though, if you do have a Y1 unit, they should work, though 1888 will require some additional patches.
2.0.2858: MOSTLY WORKS. I don't think this will boot on anything newer than a Rhea, but reliable consoles with Rhea and Elpis GPUs are plentiful, and they will boot this dashboard. I believe this is also the first dashboard that will boot Gears of War, so it's the oldest dashboard that I'd seriously try to use. This dashboard requires you to reflash your DVD drive to a pre-XGD3 drive firmware if you're downgrading a console that has a newer drive firmware, so beware of that. I recommend iXtreme 1.1 if you don't want to use a stock firmware.
2.0.4532-2.0.4548: DOES NOT BOOT. I didn't bother testing these because it's known already that these two kernels specifically don't work. Microsoft patched the JTAG exploit by blacklisting these kernels in updated bootloaders, therefore you can't use them.
2.0.4552-2.0.6770: MOSTLY WORKS. Also yes, 2.0.6770 is a real version of the blades dashboard. As I noted previously, all of these kernels will throw an E66 error if you try to boot them on a console with a DVD drive firmware after XGD3's implementation, which happened with the 2.0.13146 update. The easiest solution is to remove the DVD drive, however you can also flash the DVD drive with a pre-XGD3 firmware, and it will actually read games (so long as you flash the correct DVD key, obviously).
2.0.7357-2.0.7371: MOSTLY WORKS. Out of these three dashboards, I only tried 7371, and it was able to boot with the same issues as the Blades kernels. The solution is also the same for these dashboards, I just noted them separately because this is where the NXE dashboards start.
2.0.8498: WORKS. I know, I was surprised too, but I didn't have any issues with booting this dashboard.
2.0.8955-2.0.9199: DOES NOT BOOT. I'll just repeat what I said last time: You can tell if you patched the correct CB or not by whether or not you get a general hardware failure with the secondary error code of 0022. 8498 was the system update that fixed the JTAG hack, but these kernels seem to have changed something that only allows you to boot them with patched but non-split CBs. Testing with consoles that have patched single CBs was pretty much inconclusive, but getting the CPU key on those consoles requires you to RGH the system anyway because nobody is brave enough to port badupdate to anything below 17559.
All Kinect Dashboards: DOES NOT BOOT. I tried every single version, none of them would even try to boot.
2.0.14699-2.0.15572: DOES NOT BOOT. 14699 was the last dashboard before phat consoles got split cbs (slims had them from day one). 14717-15572 had cbs that were unique to those dashboards, and I think they only boot on those cbs.
2.0.15574: WORKS. This dashboard was the first to use the current cb versions still present in 17559, and as a result, this dashboard under the hood is EXTREMELY similar to the current version. For most slim consoles, this is the lowest you can go, not sure what the case is with Winchester boards though if anyone is even considering downgrading those.
2.0.16197-2.0.16203: WORKS (probably). This is where Metro V2 dashboards start, I only tried 2.0.16203 though because it's the last old dashboard that's even slightly worth running, and it worked without any issues.
Hopefully this is a good reference for anyone looking to downgrade a burner system or something. I've tried to be somewhat all inclusive based on what I know, even if 6717 is the only dashboard anyone cares about, and I know that works on all phats. Please don't use this info to scam people.
