ehhh... Maybe for some unexpected reason, I can't tell the detail
oh! yeah! for v2ray and ss in specific OpenWrt Build(L/E/D/E)
ennn... download file under packages folder, install through offline plugin install. BACKUP AT FIRST
sorry I'm not the developer of this plugin, I only create the backup script and add v2ray install script, ss is dumped from setting page. maybe it should belong to the DEV-Group who depreacted this one for political reason.
what I'm sure about is plugin work fine on my router, and I never add back doors. I can't guarantee the function work well under your situation or the plugin I installed maybe modified. Use it on YOUR OWN RISK!