You can turn off the automatic insertion of styles by setting the config option

htmx.config.includeIndicatorStyles

to false, and then you'd need to manually include the styles for indictators:

css
  .htmx-indicator {opacity:0;transition: opacity 200ms ease-in;}
  .htmx-indicator.htmx-request {opacity:1} 
  .htmx-indicator .htmx-request {opacity:1}