I installed OpenWRT on a Zyxel GS1900-24E. There is no final description how to install it on the device page so I oriented on other GS1900 devices. I installed initramfs version and the router booted correctly. I opened LuCI and flashed the sysupgrade image. After the report it shows the following system status but is still in initramfs mode.
In case you flashed the initramfs-kernel image to the wrong partition
The device appears to reset itself on each boot. This is because it's booting the wrong partition, namely the one that contains the initramfs image. There's no overlay filesystem. To fix this:
SSH into the switch (still using port 1 and VLAN 100).
Recent[0] versions of OpenWrt would have the equivalent tools fw_printsys, fw_setsys preconfigured for the system environment (in addition to the u-boot environment normally accessed via fw_printenv, fw_setenv). Likewise the VID100 dance should no longer be required either.
Decided to go back to Zyxel firmware as it has more hardware supported options like LACP. Do you know how to revert back? Simply upload the original firmware?
After fixing the boot partition thing everything was very easy without any VLAN100 and LuCI was directly available.... Sadly I cannot document it in the device page...