How to enable xiaomi 4a gigabit stock firmware's telnet or ssh on boot?

Does anyone know how to enable ssh or telnet on boot of xiaomi 4a gigabit?
right now I can access telnet by using https://github.com/acecilia/OpenWRTInvasion, but i want to enable it when i boot the router.
I tried the costom openwrt firmware, but the wifi is quite unstable. Thanks.

Dropbear is not installed.