The show must go on — mostly virtually but some of it live, with remote help. This spring, as a cautious reopening begins, the American Repertory Theater (A.R.T.) has been focusing on international collaborations, taking lessons from recent A.R.T. productions that managed, against the odds (and sometimes with precise global coordination and precision), to bring live theater back abroad. The popular A.R.T. Travels events will continue as a virtual series this spring, but the theater is making preparations for some upcoming, in-person performances. And it has some pertinent pandemic-era experience under its belt. On Nov. 24, the company’s revival of “Pippin” opened in Sydney, the first post-COVID production to be staged there after eight months of lockdown.