With the 1200, if I try to install anything newer, attempting to interact with it becomes sluggish/unreliable, and I have to be on my toes in order to flash it back to the 19.07.x series. Luci would work, but again, unreliable as the connection would keep dying out.
With the 3500, the system would fail to boot and I had to do the little button press thingy to gain enough access to flash it back to the 19.07.x series.
So are these two devices simply not capable of going to anything newer, or is there a trick that I just didn't come across that will make them work just fine?
With the 1200, as soon as it boots up, it's sluggish (both LuCI and SSH). I can type something via CLI and it might take a minute before it appears. I can copy/paste commands, though it's still a matter of it acknowledging that it received anything. I was able to get it back to 19.07.9 by using WinSCP to upload the sysupgrade package to /root and then flashing it from there (SSH). This is before even being able to change anything.
EA3500, I had to do the button press to get the Barry Allen flashing speed so I could TFTP into it to recover. It wouldn't complete the booting process.
I hate you (not really). I bricked my E3000 a few years back and haven't been able to recover it. I had bricked it once before but managed to revive it, but then tried to do another upgrade (using wrong firmware I think, oops) and all it does now is blink blue on the power button. Shorting pins doesn't work, and not sure how to attach wires to the serial port (WAN port) to try that method. lol
That said, I get an error message when trying to upgrade past the 19.07 series. One I'm sure you've seen mentioned plenty of times.
Device linksys,caiman not supported by this image Supported devices: linksys,wrt1200ac armada-385-linksys-caiman linksys,caiman - Image version mismatch: image 1.1, device 1.0. Please wipe config during upgrade (force required) or reinstall. Reason: Config cannot be migrated from swconfig to DSA Image check failed.
The uploaded image file does not contain a supported format. Make sure that you choose the generic image format for your platform.
Before trying it again, should this be a warning sign, or is this to be expected when flashing from 19.x and before to something newer?
I have this model as well and already had upgraded to the current stable release 22.03.3 for a probaby a week ago or so using imagebuilder sysupgrade image.
Luci is running smoothly on the EA3500 at least in my network but I do rotate the models I own around and can put it back in front of my network and check again if I experience some performance issues later tomorrow.
When I had bricked this device in the past (I don't remember the circumstances), I actually did (successfully) use the pin-short method. It is most certainly not recommended, but I got it to work (I had to use a loupe and a very small metal object to short the correct pins and avoid any accidental damage).
The warning is entirely expected.
I'm not an expert on your two device, but I do recall that a few Linksys models actually need to be flashed back to stock and then utilize a factory image to 22.03 due to a partition map change.
You weren't causing any confusion, I've just learned to be extra cautious at times. I'd rather clarify and be right than to find out that... oops, I wasn't.
When I bricked it the first time around, shorting the pins fixed it for me. I don't know if the knowledge came from my asking for help, but I do know that the image provided to me (on which pins to short) has made its way to other sites. This was back in 2012 that I asked for help (using dd-wrt at the time) and a guru named Eko provided me with an image, telling me what I needed to do. It worked.
So I was a bit sad when it didn't save my (donkey) the next time around.
To confirm, TFTP is pressing the button, connecting to 192.168.1.1 despite it not showing up in arp -a, then flashing a firmware from there? That didn't work, so flashing to 19.07 then doing it the long way around. (stock then factory)