I haven't played TS3 in a long time and when I reinstalled it found that we are now on the EA app rather than Origin. With Origin I could play offline, even if I shut down the computer and later started it up again.
Not with the EA app however. I have to start online every time the computer is rebooted. As I don't play this or any game with other's I just prefer to be offline. So my question is how do I play offline with this app?

Unfortunately, you can't without logging in at least once.
The EA App is designed to be as intrusive as possible. That's just.... EA.

It may be possible to use Origin and block the EA App update with certain tools (profanity warning), but it has been a while since the last update so I'm unsure if this still works.
Otherwise, it may be worth looking into buying the game on a different platform- either from Steam or retail discs, which are the 1.67 version of the game that isn't tied to Origin.

Thanks CardjnalSims. I was afraid of this. However I do have all the discs so if it continues to be annoying I can just have a marathon install session. It might have to get a bit more annoying for that though!

To add to something @CardinalSims said... If you try going all disc, They are avaiable as used on Amazon at fair prices. Just be careful of seller, and understand that it will be a crap shoot. You need a base game disc that is pre-Origin, and absolutely no way to know. All other discs will load to that base game disc, whether EA or Origin.