Upgrading from Chaos Calmer that doesn't support sysupgrade

I have Linksys EA4500 that runs OpenWrt Chaos Calmer (CC) without sysupgrade support (candy router flash layout).
My understanding that to move forward with Linksys EA4500 I have to boot the device using the stock firmware first and perform a regular firmware update using OpenWRT DD or LEDE factory.bin image.
Unfortunately my device has CC in both primary and backup partitions, so in any case my device boots with CC.

  1. Is there any way to upgrade my box to DD or LEDE without serial connection?
  2. My understanding that LEDE firmware is expecting a factory-like MTD flash layout. Should I restore the layout somehow? Can it be done without serial connection?

Machine model: Linksys EA4500

DISTRIB_DESCRIPTION='OpenWrt Chaos Calmer 15.05'

cat /proc/mtd
dev: size erasesize name
mtd0: 00080000 00020000 "u-boot"
mtd1: 00020000 00020000 "u-boot environment"
mtd2: 00200000 00020000 "kernel"
mtd3: 01c00000 00020000 "root"

have you tried mtd write? E3000 Upgrade -- missing bin?

my understanding is that before using mtd I have to restore the flash layout to be as factory-like.
My current layout is to fit the candy firmware and therefore doesn't fit the LEDE or stock firmware.

I am wondering if anyone has ever restored a flash layout in Linksys EA4500 without a serial connection.

Try the official TFTP recovery from Linksys using the stock firmware to see if it works. After this stock firmware is installed, you should be able to upgrade to LEDE from it.

The expected TFTP server IP could also be as documented in OpenWrt's Wiki.