Installing a specific package version on Ubuntu

On Ubuntu and potentially other Debian based distributions, you can check the available versions of a package with the apt show command

apt show -a

Example showing firefox versions

~$ apt show -a firefox
Package: firefox
Version: 87.0+build3-0ubuntu0.20.04.2
Priority: optional
Section: web
Origin: Ubuntu
Maintainer: Ubuntu Mozilla Team <ubuntu-mozillateam@lists.ubuntu.com>
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 More information
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Package: firefox
Version: 75.0+build3-0ubuntu1
Priority: optional
Section: web
Origin: Ubuntu
Maintainer: Ubuntu Mozilla Team <ubuntu-mozillateam@lists.ubuntu.com>
Bugs: https://bugs.launchpad.net/ubuntu/+filebug
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To install a specific version, use the version number

sudo apt install firefox=75.0+build3-0ubuntu1