I am using P2812 25.12.2 version with Turkish language package preinstalled from firmware selector, but then I put the config file afterwards. Then the Turkish language just disappears from system menu, I check from the software it's actually installed but not selectable.
root@OpenWrt:~# ubus call system board
{
"kernel": "6.12.74",
"hostname": "OpenWrt",
"system": "xRX200 rev 1.1",
"model": "Zyxel P-2812HNU-F1",
"board_name": "zyxel,p-2812hnu-f1",
"rootfs_type": "squashfs",
"release": {
"distribution": "OpenWrt",
"version": "25.12.2",
"firmware_url": "https://downloads.openwrt.org/",
"revision": "r32802-f505120278",
"target": "lantiq/xrx200",
"description": "OpenWrt 25.12.2 r32802-f505120278",
"builddate": "1774469393"
}
}