How to properly install new version of MonoDevelop under Ubuntu 16.04 based system?

OS and DE: Linux Mint 18.1 Cinnamon 64-bit; Ubuntu 16.04 based

Software I want to upgrade: MonoDevelop

Currently installed version:

apt-cache policy monodevelop

is:

monodevelop:
  Installed: 5.10.0.871-2
  Candidate: 5.10.0.871-2
  Version table:
 *** 5.10.0.871-2 500
        500 http://de.archive.ubuntu.com/ubuntu xenial/universe amd64 Packages
        500 http://de.archive.ubuntu.com/ubuntu xenial/universe i386 Packages
        100 /var/lib/dpkg/status

As you can see, I didn't even bother with adding the repository, and just installed it some time ago from Ubuntu Universe. So, for a longer period of time, I have no longer maintained version (deprecated) installed. I haven't used it, so it didn't bother me, but now I want to.

First, I have been instructed to install flatpak - on the official page using a PPA on the bottom of this page, which is new to me. Here I mention just a Wikipedia excerpt:

flatpak, named xdg-app until May 2016, is a software utility for software deployment, package management, and application virtualization for Linux desktop computer environments. The utility provides a sandbox environment called Bubblewrap, in which users can run applications in isolation from the rest of the system.

I considered it to be safe, so I added the PPA and installed it:

sudo add-apt-repository ppa:alexlarsson/flatpak
sudo apt-get update
sudo apt-get install flatpak

No problem here.

Problem #1:

I originally wanted to remove the old MonoDevelop with result:

Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  libart2.0-cil libgconf2.0-cil libgnome-vfs2.0-cil libgnome2.24-cil libmono-csharp4.0c-cil libmono-messaging4.0-cil
  libmono-microsoft-build-engine4.0-cil libmono-microsoft-build-framework4.0-cil libmono-microsoft-build-tasks-v4.0-4.0-cil
  libmono-microsoft-build-utilities-v4.0-4.0-cil libmono-microsoft-csharp4.0-cil libmono-microsoft-web-infrastructure1.0-cil
  libmono-system-configuration-install4.0-cil libmono-system-data-linq4.0-cil libmono-system-data-services-client4.0-cil
  libmono-system-identitymodel-selectors4.0-cil libmono-system-identitymodel4.0-cil libmono-system-messaging4.0-cil
  libmono-system-runtime-caching4.0-cil libmono-system-runtime4.0-cil libmono-system-servicemodel-activation4.0-cil
  libmono-system-servicemodel4.0a-cil libmono-system-web-extensions4.0-cil libmono-system-web-mvc3.0-cil libmono-system-web-razor2.0-cil
  libmono-system-web-webpages-deployment2.0-cil libmono-system-web-webpages-razor2.0-cil libmono-system-web-webpages2.0-cil
  libmono-system-xaml4.0-cil libmono-windowsbase4.0-cil libmono-xbuild-tasks4.0-cil mono-xbuild
Use 'sudo apt autoremove' to remove them.
The following additional packages will be installed:
  libwebkit1.1-cil monodoc-browser
Suggested packages:
  monodoc-webkit-manual
The following packages will be REMOVED:
  monodevelop*
The following NEW packages will be installed:
  libwebkit1.1-cil monodoc-browser
0 upgraded, 2 newly installed, 1 to remove and 4 not upgraded.
Need to get 83.2 kB of archives.
After this operation, 32.8 MB disk space will be freed.
Do you want to continue? [Y/n] n
Abort.

Question #1:

Should I proceed with the removal?

Problem #2:

When trying to install it as instructed:

flatpak install --user --from https://mono-project.azureedge.net/repo/monodevelop.flatpakref

I am asked a maybe important question:

This application depends on runtimes from:
  http://sdk.gnome.org/repo/
Configure this as new remote 'gnome' [y/n]: ^C

Question #2:

What does the question:

Configure this as new remote 'gnome' ?

even mean? In order for me to decide yes / no.

Solution

I tested the solution in a fresh installed VM:

Should I proceed with the removal?:

Yes, proceed with the removal of old version.
```
sudo apt-get purge monodevelop
sudo apt-get --purge autoremove
```
will do just fine.

What does the question even mean? In order for me to decide yes / no.

First, I answered No. It resulted in error:

error: The Application com.xamarin.MonoDevelop/x86_64/stable requires the runtime org.freedesktop.Platform/x86_64/1.4 which is not installed

It obviously needs it, so just answer Yes, twice:

This application depends on runtimes from:
  http://sdk.gnome.org/repo/
Configure this as new remote 'gnome' [y/n]: y

Installing: com.xamarin.MonoDevelop/x86_64/stable
Required runtime for com.xamarin.MonoDevelop/x86_64/stable (org.freedesktop.Platform/x86_64/1.4) is not installed, searching...
Found in remote gnome, do you want to install it? [y/n]: y

Installing: org.freedesktop.Platform/x86_64/1.4 from gnome

8 delta parts, 59 loose fetched; 114542 KiB transferred in 54 seconds                                                
Installing: org.freedesktop.Platform.Locale/x86_64/1.4 from gnome

5 metadata, 1 content objects fetched; 13 KiB transferred in 4 seconds                                               
Installing: com.xamarin.MonoDevelop/x86_64/stable from com.xamarin.MonoDevelop-1-origin

898 metadata, 3279 content objects fetched; 152977 KiB transferred in 39 seconds

You can run it now from terminal using:
```
flatpak run com.xamarin.MonoDevelop
```