This article covers methods to fix #Ubuntu #error "Some index files failed to download". You can resolve this error by copying the contents of the sources list file from another functional Ubuntu system and paste them into your system's sources list file.
To install community-supported #software packages, proprietary packages, and packages not available under a completely free license, you might consider enabling the following repositories:
1. Universe – Community-maintained free and open-source software.
2. Restricted – Proprietary drivers for devices.
3. Multiverse – Software restricted by copyright or legal issues.
To enable these #repositories, invoke the commands below:
$ sudo add-apt-repository restricted
$ sudo add-apt-repository multiverse
$ sudo add-apt-repository universe
Then update your package lists:
$ sudo apt update