Updating a LinkSys WRT19000ACS from 18.06 to 22.03

Installing and Using OpenWrt
1

I get this: The uploaded image file does not contain a supported format. Make sure that you choose the generic image format for your platform.

It's running: Powered by LuCI openwrt-18.06 branch (git-18.228.31946-f64b152) / OpenWrt 18.06.1 r7258-5eb055306f

I downloaded this: https://downloads.openwrt.org/releases/22.03.2/targets/mvebu/cortexa9/openwrt-22.03.2-mvebu-cortexa9-linksys_wrt1900ac-v1-squashfs-sysupgrade.bin

Please can you tell me which image I need and the link to obtain it?

2

You should probably force it, don't however go to 22.03, but 23.05 RC, pretty sure all the mvebu 22.03s have seriously crippled wifi.

3

Take a backup first. Do NOT save config over reflash. You will need to recreate your network config from scratch because the platform has moved to DSA.
See these relevant wiki links