How can I remove the asterisk for required fields programatically?
This can be removed from the theme.  I'm using a Bootstrap subtheme, so in my case I copied form-element-label-html.twig from the bootstrap templates directory into my subtheme's templates directory, then changed the following line:

  {%- if required -%}
    &lt;span class="form-required"&gt;*&lt;/span&gt;
  {%- endif -%}


To:

  {%- if required -%}
    {# &lt;span class="form-required"&gt;*&lt;/span&gt; #}
  {%- endif -%}


Clear caches and it's done.