But it regurgitates Stackoverflow with sub 100% accuracy, and then you need to spend time investigating in what went wrong/trying to fix it

Since it is bespoke boilerplate, it isn't "just" documentation or Stackoverflow. Take this example, I gave it a library, I gave it custom names for everything, and the result is pretty time-saving:

Prompt:

     Create html using the bootstrap 5 library, create form with a fieldset (title: "Filter") inside with the following select option/label groups: 
      - Department    
      - Year 
      - Invoice Source 
      - Invoice Destination 
     
     Then two inputs/labels for start date and end date, and a submit button. Only include one example in each of the select options and no page boilerplate.

Result:

       <form>
       <fieldset>
         <legend>Filter</legend>
         <div class="mb-3">
           <label for="department" class="form-label">Department</label>
           <select class="form-select" id="department">
             <option selected>Choose department</option>
             <option value="1">Sales</option>
           </select>
         </div>
         <div class="mb-3">
           <label for="year" class="form-label">Year</label>
           <select class="form-select" id="year">
             <option selected>Choose year</option>
             <option value="2022">2022</option>
           </select>
         </div>
         <div class="mb-3">
           <label for="source" class="form-label">Invoice Source</label>
           <select class="form-select" id="source">
             <option selected>Choose source</option>
             <option value="1">Email</option>
           </select>
         </div>
         <div class="mb-3">
           <label for="destination" class="form-label">Invoice Destination</label>
           <select class="form-select" id="destination">
             <option selected>Choose destination</option>
             <option value="1">Customer</option>
           </select>
         </div>
         <div class="row">
           <div class="col-md-6">
             <label for="start-date" class="form-label">Start Date</label>
             <input type="date" class="form-control" id="start-date">
           </div>
           <div class="col-md-6">
             <label for="end-date" class="form-label">End Date</label>
             <input type="date" class="form-control" id="end-date">
           </div>
         </div>
         <div class="d-grid mt-3">
           <button type="submit" class="btn btn-primary">Filter</button>
         </div>
       </fieldset>
     </form>