I was following this thread to install wine, but after I added the suggested repository and reloaded the sources list the following error message appeared:
W:The repository 'http://extras.ubuntu.com/ubuntu xenial Release' does not have a Release file.,
W:Data from such a repository can't be authenticated and is therefore potentially dangerous to use.,
W:See apt-secure(8) manpage for repository creation and user configuration details.,
W:The repository 'http://ppa.launchpad.net/ubuntu-audio-dev/ppa/ubuntu xenial Release' does not have a Release file.,
W:Data from such a repository can't be authenticated and is therefore potentially dangerous to use.,
W:See apt-secure(8) manpage for repository creation and user configuration details.,
E:Failed to fetch http://extras.ubuntu.com/ubuntu/dists/xenial/main/source/Sources 404 Not Found [IP: 2001:67c:1360:8c01::23 80],
E:Failed to fetch http://ppa.launchpad.net/ubuntu-audio-dev/ppa/ubuntu/dists/xenial/main/binary-amd64/Packages 404 Not Found,
E:Some index files failed to download. They have been ignored, or old ones used instead.
What is wrong here? Probably the messages are clear for those who can read them, but I do not want to make things messier.
Best Answer
As for does a PPA support you release
If I want to add a PPA that a howto, or web.post tells me will work with Ubuntu, some basic steps to follow could be
eg. https://launchpad.net/~ubuntu-audio-dev/+archive/ubuntu/ppa and read the developers notes. For my example the notes are rather vague. However scrolling down I can see in the "Overview of published Packages" section a list of packages, dates of upload, uploaded by etc. This is your first clue, most dates are 2010-2012, with only a single 2013.
Your release is Ubuntu 16.04, or the Ubuntu release from 2016 April. This is a long time past 2013, so you've detected a problem here.
eg. http://ppa.launchpad.net/ubuntu-audio-dev/ppa/ubuntu/dists/ I use this myself quite often (as it involves less reading, which is why it was mentioned in the first comment). What you'll see is a list of folders for each supported release. Ubuntu 16.04 is Xenial, so to support xenial there must be a folder for xenial, but there isn't. The latest folder is 'raring' or 13.04, the 2013 upload in the prior section. Problem detected here too.
If this for my own machine, or a box I valued (eg. production)
the main PPA page is a must, as I tend to look there at the way its written, how it's written by (even if I don't know the people, in my example its a team of 90 'active' members which gives a good feeling) and try and see if I trust this source. Here I think the PPA looks good, except it appears old...
As for replacement sources
I can't help here sorry. I don't know why you added the PPA, so I don't know what you are looking for so can't find a replacement.
If however instructions that told you to add this PPA are from an older release, check you actually need it. For example I added a PPA in Ubuntu 14.04 LTS, and 16.04 LTS for Redshift because I found the night color change helpful. Ubuntu 17.10 & 18.04 LTS however don't need it anymore; having the desired function by default.