One of 2021's big themes for No Man's Sky has been expeditions, with highlights including a Mass Effect crossover that saw the Normandy make an appearance. These events, however, run for a limited time, and a press release from Hello Games acknowledges that «this very busy year, and the limited-time nature of the expeditions, has meant that it has been difficult for some people to participate in them.»
Thus they're all coming back over the festive period, and yes that includes Mass Effect:
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