您可能会遇到延迟，因为 Bootstrap 在导航栏的show之前添加了一个collapsing类，以提供对动画的更多控制。
如果您正在寻求平稳过渡，我相信这可能会有所帮助：https://www.bootply.com/rPqvbgcCVj

body {
  overflow-x: hidden;
  -webkit-transition: margin .3s ease;
  -moz-transition: margin .3s ease;
  -o-transition: margin .3s ease;
  transition: margin .3s ease;
  width: 100%;
  margin: 0;
  font-family: -apple-system,
    BlinkMacSystemFont,
    "Segoe UI",
    Roboto,
    "Helvetica Neue",
    Arial,
    sans-serif;
  font-size: 1rem;
  font-weight: 400;
  line-height: 1.5;
  color: #212529;
  background-color: #fff;
}

.navbar-light .navbar-nav .nav-link {
  padding-right: 1.5rem;
  padding-left: 1.5rem;
  position: relative;
}

.navbar .menu-item.menu-item-has-children > .nav-link:after {
  content: "";
  width: 0;
  height: 0;
  border-style: solid;
  position: absolute;
  right: 0;
  top: 50%;
  -ms-transform: translateY(-50%);
  -webkit-transform: translateY(-50%);
  transform: translateY(-50%);
  border-width: 4px 4px 0px 4px;
  border-color: #007bff transparent transparent transparent;
}
/* Added the following code and removed previous code */
.collapsing {
  transform: translateX(0%);
}

@media (max-width: 991px) {
  body.active {
    overflow: hidden;
    height: 100%;
    width: 100%;
    margin-left: -280px;
  }
  .collapse.active {
    transform: translateX(0%);
  }

  .navbar-collapse {
    position: fixed;
    right: 0px;
    top: 0px;
    display: block;
    transform: translateX(100%);
    height: 100vh;
    width: 280px;
    transition: transform .3s ease;
    overflow-y: scroll;
    background: #fff;
  }
  /* Added the following code */
  .active.collapsing {
    transform: translateX(0%);
  }

  .navbar .menu-item.menu-item-has-children > .nav-link:after {
    right: 1.5rem;
  }
}

对于想要修复bootstrap 5 offcanvas延迟的用户，这可以帮助您：

.offcanvas {
  transition : transform 0.15s cubic-bezier(0.165, 0.84, 0.44, 1), box-shadow 0s ease;
}