HTML

modal footer align left bootstrap

<div class="modal-footer justify-content-between">                    
   <button type="submit" class="btn btn-danger">Delete</button>                                    
   <div>
       <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
       <button type="submit" class="btn btn-primary">Save changes</button>
   </div>  
</div>

bootstrap modal footer text left align

<div class="modal-footer">
     <button type="button" class="btn btn-primary mr-auto">Save changes</button>
     <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
</div>