To Change Mirror Manually You have to change your mirror address in /etc/apt/sources.list

After that run the apt update command

Bardia Moshiri Mirror in Iran

For Ubuntu 22.04

#Ubuntu Main Repositories

deb http://ubuntu.bardia.tech/ubuntu/ jammy main restricted universe multiverse

deb-src http://ubuntu.bardia.tech/ubuntu/ jammy main restricted universe multiverse

Ubuntu Update Repositories

deb http://ubuntu.bardia.tech/ubuntu/ jammy-updates main restricted universe multiverse

deb-src http://ubuntu.bardia.tech/ubuntu/ jammy-updates main restricted universe multiverse

For Ubuntu 21.10

#Ubuntu Main Repositories

deb http://ubuntu.bardia.tech/ubuntu/ impish main restricted universe multiverse

deb-src http://ubuntu.bardia.tech/ubuntu/ impish main restricted universe multiverse

#Ubuntu Update Repositories

deb http://ubuntu.bardia.tech/ubuntu/ impish-updates main restricted universe multiverse

deb-src http://ubuntu.bardia.tech/ubuntu/ impish-updates main restricted universe multiverse

For Ubuntu20.04

#Ubuntu Main Repositories

deb http://ubuntu.bardia.tech/ubuntu/ focal main restricted universe multiverse

deb-src http://ubuntu.bardia.tech/ubuntu/ focal main restricted universe multiverse

Ubuntu Update Repositories

deb http://ubuntu.bardia.tech/ubuntu/ focal-updates main restricted universe multiverse

deb-src http://ubuntu.bardia.tech/ubuntu/ focal-updates main restricted universe multiverse

For Ubuntu 18.04

#Ubuntu Main Repositories

deb http://ubuntu.bardia.tech/ubuntu/ bionic main restricted universe multiverse

deb-src http://ubuntu.bardia.tech/ubuntu/ bionic main restricted universe multiverse

Ubuntu Update Repository

deb http://ubuntu.bardia.tech/ubuntu/ bionic-updates main restricted universe multiverse

deb-src http://ubuntu.bardia.tech/ubuntu/ bionic-updates main restricted universe multiverse

For other distros change OS Codename after mirror URL. For example 16.04 is xenial which should be replaced with bionic or focal

The mirror is verified by Canonical themselves

So it can be selected through Ubuntu settings