Render partial in Stimulus.md

 fetch(href, {
      headers: {
        Accept: "text/vnd.turbo-stream.html",
      },
    })
      .then(r => r.text())
      .then(html => Turbo.renderStreamMessage(html))
//  optionally reflect the url    .then(_ => history.replaceState(history.state, "", href))

import { Controller } from '@hotwired/stimulus'

export default class extends Controller {
  static values = {
    src: String,
  }

  connect() {
    fetch(this.srcValue, {
      headers: {
        Accept: "text/vnd.turbo-stream.html",
      },
    }).then(r => r.text())
      .then(html => Turbo.renderStreamMessage(html))
  }
}

async uploadFileToServer(file) {
  // ...
  const response = await fetch("/test/upload", {
    // ...
  })
  
  const html = await response.text()
  Turbo.renderStreamMessage(html)
}

Turbo.visit(url, { frame: '_top', action: 'advance' })