There is no modern equivalent for Frontier these days.
What about Freelancer? Or on iOS there Galaxy On Fire and GOF2, which is amazing. EV: Nova is another very good space combat/trading game, and for online players there is of course Eve Online and also Outer Empires is very good.
Note that I've never actually played Elite or Frontier, so I'm just going on what I've read about the game.
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moto
