I think that this will work, at least it worked in my computer locally with HiGHS.
model = direct_model(Gurobi.Optimizer())
lp = read_from_file("model.lp")
MOI.copy_to(backend(model), lp)
optimize!(model)
Other possibility is to call MOI.optimize! directly
model = direct_model(Gurobi.Optimizer())
lp = read_from_file("model.lp")
MOI.optimize!(backend(model), lp)