According to what I've found this claim is true- Trump is planning to build a monument reminiscent of the arc de triomphe to commemorate the 250th anniversary of the country's founding. The location chosen for this structure is across the bridge from the Lincoln Memorial to serve as a ceremonial entrance to the capitol city. According to BBC, the project will still require congressional approval and will have to be organized by the National Capital Planning Commission in order to actually be completed. This reality means that it will likely be nowhere near construction by the time the 250th anniversary comes around. Critics see this as an extended effort to establish his permanence in office, these dramatic renovations to the White House don't necessarily reflect a willingness to hand over power once his term is complete. Why add a massive ballroom, and an arch paid for by his supporters, if he's not planning on sticking around long term? The Guardian's article discussing this brought to light that the arc de triomphe was built in commemoration of emperor Napoleon's birthday. The fact that an arch will be built using Trump's supporters funds that is reminiscent of a famously tyrannical leader's monument is understandably concerning because of the shared symbolism. Presidents are typically memorialized for their great deeds long after they leave office, the connotation of a president using their influence to establish a permanent monument during their term could be seen as a slightly unorthodox.
