There are some routers with OEM fork of OpenWRT that allow you to flash stock openwrt without any obstacles and by easily dropping the image blob in the web UI - just easy as upgrading the firmware from stock openwrt.
Granted, not exactly what you wished for, but pretty close.
Granted, not exactly what you wished for, but pretty close.
The time to do this is <5 minutes. One such router I personally know of is GL.iNet GL-MT6000: https://openwrt.org/toh/gl.inet/gl-mt6000