It still has a memory leak without any widgets. So just the code to initialize and register the display driver and input device followed by the main event loop. Every call to lv_tick_inc allocates memory that never gets freed and since it is being called every 5ms that is a big problem.
As you can see here lv_tick_inc merely increments a variable so it itself is not the problem. lv_task_handler only refreshes the display after time passes so that’s why the memory leak goes away when you don’t call lv_tick_inc.
I suggest setting a breakpoint on lv_mem_alloc and checking what keeps allocating memory multiple times.
I see two possibilities, first there is something wrong in the simple example code or second there is a bug in the LVGL library. The second case seems less likely since I have not been able to find any other reports of this issue. That leads me to believe that there must be something being done incorrectly in the example code, so before I head down the path of debugging lv_mem_alloc do you see anything that is wrong with this code?