Yes, it can; it has deployed peacekeeping missions without Security Council signoff (UNEF I), by the UNGA after France and the UK vetoed action in the UNSC, it adopted broad sanctions against South Africa, through the UNGA, after a triple veto by the US, UK. and France.
The UNGA has taken various action, including expelling Russia from the Human Rights Council, in respect to the Russo-Ukrainian war in a process starting with a Russian Security Council veto.
The common underlying factor in all of these is the UNGA “Uniting for Peace” resolution pit forward by the US during the Korean War because, while dodged initially in that situation because of the Soviet boycott of the UN over other issues, the problem with letting the Security Council veto be the end of the story was made very clear in that context.
