Big SEO issue URGENT

i do not see your page – but you can use the filter in this case: avf_customize_heading_settings

This filter exists in a lot of ALB Elements to change the heading tag: Link

on time line there are two possibilites to influence the date and the title
And you can even add an additional Class to these tags:
Put this to your child-theme functions.php

function my_avf_customize_heading_settings( array $args, $context, array $extra_args = array()){

// this is for the date 
  if( $context == 'avia_sc_timeline' && is_array( $extra_args ) && in_array( 'date', $extra_args ) )
  {
    $args['heading'] = 'h3';            
    $args['extra_class'] = 'custom-date-class';   
  }

// this is for the title 
  if( $context == 'avia_sc_timeline' && is_array( $extra_args ) && in_array( 'title', $extra_args ) )
  {
    $args['heading'] = 'h2';            
    $args['extra_class'] = 'custom-title-class';   
  } 
  
  return $args;
}
add_filter( 'avf_customize_heading_settings', 'my_avf_customize_heading_settings', 10, 3 );

so you had to wait til a mod is here.