Raspberry Pi4 lower MTU

How to permanently change MTU on eth0 interface on RPi4 with DietPi 8.8? I can do it with ifconfig eth0 mtu 1440 but I need it to be persistent.

Welcome to our community

I guess this will help you How to change MTU size in Linux

Thanks. This is indeed the solution which works.

interface "eth0" {
default interface-mtu 1440;
supersede interface-mtu 1440;