Upgrading TpLink Archer C2 AC750 v1 to latest sysupgrade package fails

I'm struggling to get openwrt going on this old archer c2

At first I tried prepping my own package and flashing it with tftp as per the instructions on this page

That seemed to fail, the router would download the package from the tftp server and then nothing, even when left alone overnight.

So then i flashed the recovery image found here (link also found on the previously mentioned page)

That worked like a charm

Then i tried to sysupgrade to the latest supported version (23.05.3) found here

The sysupgrade seems to do its thing but the router becomes completely unresponsive, i can recovery mode back to the other version just fine.

opkg update fails with:
Signature check failed.
Remove wrong Signature file.

output of ubus call system board; cat /etc/openwrt_release:

"kernel": "4.4.14",
"hostname": "OpenWrt",
"system": "MediaTek MT7620A ver:2 eco:6",
"model": "TP-Link Archer C2",
"release": {
"distribution": "OpenWrt",
"version": "Bleeding Edge",
"revision": "50020",
"codename": "designated_driver",
"target": "ramips\/mt7620",
"description": "OpenWrt Designated Driver 50020"
DISTRIB_DESCRIPTION='OpenWrt Designated Driver 50020'


Note that you are using some non-release OpenWRT, so you need to reset configuration when installing latest sysupgrade.
Worth backing up configuration, then manually restoring customization to new config files via luci.
Also save opkg list-installed - it may keep some extra packages you had in that custom distro.
For long-term maintenance install luci-app-attendedsysypgrade to have package upgrades go directly to rootfs and never get duplicates in overlay.

... if it doesn't work, upgrade in steps, going up one release at a time, resetting the settings every time.