I removed `deb http://ppa.launchpad.net/nginx/stable/ubuntu zesty main` from `/etc/apt/sources.list` (that would, presumably, switch ppa off?), ran `sudo apt update` and then `sudo apt install nginx-extras`. Here is the result:
```
The following packages have unmet dependencies:
nginx-extras : Depends: libnginx-mod-http-auth-pam (= 1.12.1-0ubuntu2) but 1.12.1-0+zesty0 is to be installed Depends: libnginx-mod-http-cache-purge (= 1.12.1-0ubuntu2) but it is not going to be installed Depends: libnginx-mod-http-dav-ext (= 1.12.1-0ubuntu2) but 1.12.1-0+zesty0 is to be installed Depends: libnginx-mod-http-echo (= 1.12.1-0ubuntu2) but 1.12.1-0+zesty0 is to be installed Depends: libnginx-mod-http-fancyindex (= 1.12.1-0ubuntu2) but it is not going to be installed Depends: libnginx-mod-http-geoip (= 1.12.1-0ubuntu2) but 1.12.1-0+zesty0 is to be installed Depends: libnginx-mod-http-headers-more-filter (= 1.12.1-0ubuntu2) but it is not going to be installed Depends: libnginx-mod-http-image-filter (= 1.12.1-0ubuntu2) but 1.12.1-0+zesty0 is to be installed Depends: libnginx-mod-http-lua (= 1.12.1-0ubuntu2) but it is not going to be installed Depends: libnginx-mod-http-perl (= 1.12.1-0ubuntu2) but it is not going to be installed Depends: libnginx-mod-http-subs-filter (= 1.12.1-0ubuntu2) but 1.12.1-0+zesty0 is to be installed Depends: libnginx-mod-http-uploadprogress (= 1.12.1-0ubuntu2) but it is not going to be installed Depends: libnginx-mod-http-upstream-fair (= 1.12.1-0ubuntu2) but 1.12.1-0+zesty0 is to be installed Depends: libnginx-mod-http-xslt-filter (= 1.12.1-0ubuntu2) but 1.12.1-0+zesty0 is to be installed Depends: libnginx-mod-mail (= 1.12.1-0ubuntu2) but 1.12.1-0+zesty0 is to be installed Depends: libnginx-mod-nchan (= 1.12.1-0ubuntu2) but it is not going to be installed Depends: libnginx-mod-stream (= 1.12.1-0ubuntu2) but 1.12.1-0+zesty0 is to be installed Depends: nginx-common (= 1.12.1-0ubuntu2) but 1.12.1-0+zesty0 is to be installed
E: Unable to correct problems, you have held broken packages.
```
I removed `deb http:// ppa.launchpad. net/nginx/ stable/ ubuntu zesty main` from `/etc/apt/ sources. list` (that would, presumably, switch ppa off?), ran `sudo apt update` and then `sudo apt install nginx-extras`. Here is the result: mod-http- auth-pam (= 1.12.1-0ubuntu2) but 1.12.1-0+zesty0 is to be installed
Depends: libnginx- mod-http- cache-purge (= 1.12.1-0ubuntu2) but it is not going to be installed
Depends: libnginx- mod-http- dav-ext (= 1.12.1-0ubuntu2) but 1.12.1-0+zesty0 is to be installed
Depends: libnginx- mod-http- echo (= 1.12.1-0ubuntu2) but 1.12.1-0+zesty0 is to be installed
Depends: libnginx- mod-http- fancyindex (= 1.12.1-0ubuntu2) but it is not going to be installed
Depends: libnginx- mod-http- geoip (= 1.12.1-0ubuntu2) but 1.12.1-0+zesty0 is to be installed
Depends: libnginx- mod-http- headers- more-filter (= 1.12.1-0ubuntu2) but it is not going to be installed
Depends: libnginx- mod-http- image-filter (= 1.12.1-0ubuntu2) but 1.12.1-0+zesty0 is to be installed
Depends: libnginx- mod-http- lua (= 1.12.1-0ubuntu2) but it is not going to be installed
Depends: libnginx- mod-http- perl (= 1.12.1-0ubuntu2) but it is not going to be installed
Depends: libnginx- mod-http- subs-filter (= 1.12.1-0ubuntu2) but 1.12.1-0+zesty0 is to be installed
Depends: libnginx- mod-http- uploadprogress (= 1.12.1-0ubuntu2) but it is not going to be installed
Depends: libnginx- mod-http- upstream- fair (= 1.12.1-0ubuntu2) but 1.12.1-0+zesty0 is to be installed
Depends: libnginx- mod-http- xslt-filter (= 1.12.1-0ubuntu2) but 1.12.1-0+zesty0 is to be installed
Depends: libnginx-mod-mail (= 1.12.1-0ubuntu2) but 1.12.1-0+zesty0 is to be installed
Depends: libnginx-mod-nchan (= 1.12.1-0ubuntu2) but it is not going to be installed
Depends: libnginx-mod-stream (= 1.12.1-0ubuntu2) but 1.12.1-0+zesty0 is to be installed
Depends: nginx-common (= 1.12.1-0ubuntu2) but 1.12.1-0+zesty0 is to be installed
```
The following packages have unmet dependencies:
nginx-extras : Depends: libnginx-
E: Unable to correct problems, you have held broken packages.
```