The standard, and recommended way to install software in Debian based distributions, is to install from the official repositories.
There’s a lot of “advice” on the Internet that recommend using PPAs, but much of that advice fails to mention the disadvantages of PPAs:
Security: To what extent do you trust the PPA maintainer? By enabling a PPA you are effectively giving the PPA maintainer access to the core of your operating system.
Stability: Software packages provided by PPAs is often untested prior to being made public.
Support: Typically there is no end user support provided by the PPA.
Compatibility: Compatibility testing of PPA software is often minimal or non-existent.
In short, if there’s a problem with a PPA package, then you’re pretty much on your own to fix it.
Once you have uninstalled Audacity, and removed or disabled the PPA, then installing the official repository version of Audacity can be done from a Terminal window with these commands (and follow the on-screen prompts):
Another possibility is that the PPA is recorded in its own file under /etc/apt/sources.list.d/. It might appear as a file named like the-repository-name.list.
If you remove that file and refresh the APT cache you should be able to install your distribution’s default version of Audacity.