@wilsonge

There are still a few problems. My example here is the module edit page.

When modifying a class like
.control-group .control-label line 1649
with a float:right; instead of left, you are overriding only one aspect of the class loaded before.

We have line 391

  .control-group .control-label {
    float: left;
    width: 220px;
    padding-top: 5px;
    padding-right: 5px;
    text-align: left; }

Therefore, a text-align: right; has to be added in the overriding class.
Once corrected, we have

Also for .controls class line 1654
we should have
.control-group .controls {
margin-right: 0;
margin-left: 0;
}
NOTE: _this one will not work when editing Publishing in an article edit for the calendar field and select user field
we may need for that a new class in rtl

.field-calendar {
	float: right; }

and

.field-user-wrapper {
  float:right; }

Now looks better, but we still have some issues

1. The text near the switcher is not placed correctly
   I.e. we need to modify /media/system/webcomponents/css/joomla-field-switcher.css
   Take off left: 10px;
   and change line 64 and before 84 to

  joomla-field-switcher .switcher-labels {
    position: relative; }
    joomla-field-switcher .switcher-labels span {
      position: absolute;
      top: 0;
      color: #868e96;
      visibility: hidden;
      opacity: 0;
      -webkit-transition: all .2s ease-in-out;
      transition: all .2s ease-in-out; }
      joomla-field-switcher .switcher-labels span.active {
        visibility: visible;
        opacity: 1;
        -webkit-transition: all .2s ease-in-out;
        transition: all .2s ease-in-out; }
      [dir="rtl"] joomla-field-switcher .switcher-labels span {
        right: 10px; }
      [dir="ltr"] joomla-field-switcher .switcher-labels span {
        left: 10px; }

We get

2. Remains to take care of the tip
   We also need a new class for .form-text
   with a float:right; to override the class in bootstrap.css line 1430

and that page is now solved

These should solve the similar problems elsewhere in the template.

Sorry, I have no idea how to use sass and scss. A tuto for that would be nice.

@wilsonge
Making PR now.

#21206