When I follow the instructions on updating MONO I get a lot of held back packages trying to update:
The following packages have been kept back:
libglade2.0-cil libglade2.0-cil-dev libglib2.0-cil libglib2.0-cil-dev
libgtk2.0-cil libgtk2.0-cil-dev libmono-2.0-dev libmono-accessibility4.0-cil
libmono-cairo4.0-cil libmono-cecil-private-cil libmono-cil-dev
libmono-codecontracts4.0-cil libmono-compilerservices-symbolwriter4.0-cil
libmono-corlib2.0-cil libmono-corlib4.0-cil libmono-corlib4.5-cil
libmono-csharp4.0c-cil libmono-custommarshalers4.0-cil
libmono-data-tds4.0-cil libmono-db2-1.0-cil libmono-debugger-soft4.0a-cil
Furthermore in other repos I often don't find Trusty, eg MonoDevelop 4.0 PPA | launchpad.net
or Trusty is the oldest supported (eg The main PPA for supported PHP versions with many PE | launchpad.net)
The problem is, 14.04 seems to be the last version that had support for purchasing software through Software Center as I recall... If I upgrade how can I backup packages that were bought from Ubuntu Store? It's quite surprising that Ubuntu doesn't want to make money on the store anymore and reading some questions it appears installs may not run after running upgrade: Ubuntu Software Center Purchase | Ask Ubuntu
