Choose a mirror close to your server to download from:

https://downloads.mariadb.org/mariadb/repositories/#

Here are the commands to install MariaDB 10.4 from the MariaDB repository:

1. DigitalOcean mirrors for Ubuntu 20.04 “focal”

Amsterdam

https://downloads.mariadb.org/mariadb/repositories/#distro_release=focal–ubuntu_focal&mirror=digitalocean-ams&version=10.4

$ sudo apt-get install software-properties-common
$ sudo apt-key adv --fetch-keys 'https://mariadb.org/mariadb_release_signing_key.asc'
$ sudo add-apt-repository 'deb [arch=amd64,arm64,ppc64el] http://ams2.mirrors.digitalocean.com/mariadb/repo/10.4/ubuntu focal main'

Once the key is imported and the repository added you can install MariaDB 10.4 from the MariaDB repository with:

$ sudo apt update
$ sudo apt install mariadb-server

New York

https://downloads.mariadb.org/mariadb/repositories/#distro_release=focal–ubuntu_focal&mirror=digitalocean-nyc&version=10.4

$ sudo apt-get install software-properties-common
$ sudo apt-key adv --fetch-keys 'https://mariadb.org/mariadb_release_signing_key.asc'
$ sudo add-apt-repository 'deb [arch=amd64,arm64,ppc64el] http://nyc2.mirrors.digitalocean.com/mariadb/repo/10.4/ubuntu focal main'

Once the key is imported and the repository added you can install MariaDB 10.4 from the MariaDB repository with:

$ sudo apt update
$ sudo apt install mariadb-server

San Francisco

https://downloads.mariadb.org/mariadb/repositories/#distro_release=focal–ubuntu_focal&mirror=digitalocean-sfo&version=10.4

$ sudo apt-get install software-properties-common
$ sudo apt-key adv --fetch-keys 'https://mariadb.org/mariadb_release_signing_key.asc'
$ sudo add-apt-repository 'deb [arch=amd64,arm64,ppc64el] http://sfo1.mirrors.digitalocean.com/mariadb/repo/10.4/ubuntu focal main'

Once the key is imported and the repository added you can install MariaDB 10.4 from the MariaDB repository with:

$ sudo apt update
$ sudo apt install mariadb-server

2. DigitalOcean mirrors for Ubuntu 18.04 LTS “bionic”

New York

https://downloads.mariadb.org/mariadb/repositories/#mirror=digitalocean-nyc

$ sudo apt-get install software-properties-common
$ sudo apt-key adv --fetch-keys 'https://mariadb.org/mariadb_release_signing_key.asc'
$ sudo add-apt-repository 'deb [arch=amd64,arm64,ppc64el] http://nyc2.mirrors.digitalocean.com/mariadb/repo/10.4/ubuntu bionic main'

Once the key is imported and the repository added you can install MariaDB 10.4 from the MariaDB repository with:

$ sudo apt update
$ sudo apt install mariadb-server

Amsterdam

https://downloads.mariadb.org/mariadb/repositories/#mirror=digitalocean-ams

$ sudo apt-get install software-properties-common
$ sudo apt-key adv --fetch-keys 'https://mariadb.org/mariadb_release_signing_key.asc'
$ sudo add-apt-repository 'deb [arch=amd64,arm64,ppc64el] http://ams2.mirrors.digitalocean.com/mariadb/repo/10.4/ubuntu bionic main'

Once the key is imported and the repository added you can install MariaDB 10.4 from the MariaDB repository with:

$ sudo apt update
$ sudo apt install mariadb-server

San Francisco

https://downloads.mariadb.org/mariadb/repositories/#mirror=digitalocean-sfo

$ sudo apt-get install software-properties-common
$ sudo apt-key adv --fetch-keys 'https://mariadb.org/mariadb_release_signing_key.asc'
$ sudo add-apt-repository 'deb [arch=amd64,arm64,ppc64el] http://sfo1.mirrors.digitalocean.com/mariadb/repo/10.4/ubuntu bionic main'

Once the key is imported and the repository added you can install MariaDB 10.4 from the MariaDB repository with:

$ sudo apt update
$ sudo apt install mariadb-server

REFERENCES

https://downloads.mariadb.org/mariadb/repositories/#
https://phoenixnap.com/kb/how-to-install-mariadb-ubuntu