Are there alternatives for striptags filter?
I am vehemently against things like render-array|render|striptags etc. It feels very unnatural and un-Drupal. What you should do is create a field template that has no markup.

For example, either in field.html.twig which would affect all fields, or in field--field-name.html.twig or more specific variants, you can do this:

{#
/**
* @file
* Theme override to remove all field markup.
*/
#}

{% spaceless %}
{% for item in items %}
  {{ item.content }}
{% endfor %}
{% endspaceless %}


This will always render that field with no markup.