已自行解决。

结合开源代码和 F12 报错信息，判定鉴权过程出错导致无法播放

下面是相关的源代码

func serveCheckAuth(c *gin.Context) {
	data, err := os.ReadFile(filepath.Join(util.WorkingDir, "stage/auth.html"))
	if nil != err {
		logging.LogErrorf("load auth page failed: %s", err)
		c.Status(500)
		return
	}

	tpl, err := template.New("auth").Parse(string(data))
	if nil != err {
		logging.LogErrorf("parse auth page failed: %s", err)
		c.Status(500)
		return
	}

	keymapHideWindow := "⌥M"
	if nil != (*model.Conf.Keymap)["general"] {
		switch (*model.Conf.Keymap)["general"].(type) {
		case map[string]interface{}:
			keymapGeneral := (*model.Conf.Keymap)["general"].(map[string]interface{})
			if nil != keymapGeneral["toggleWin"] {
				switch keymapGeneral["toggleWin"].(type) {
				case map[string]interface{}:
					toggleWin := keymapGeneral["toggleWin"].(map[string]interface{})
					if nil != toggleWin["custom"] {
						keymapHideWindow = toggleWin["custom"].(string)
					}
				}
			}
		}
		if "" == keymapHideWindow {
			keymapHideWindow = "⌥M"
		}
	}
	model := map[string]interface{}{
		"l0":                     model.Conf.Language(173),
		"l1":                     model.Conf.Language(174),
		"l2":                     template.HTML(model.Conf.Language(172)),
		"l3":                     model.Conf.Language(175),
		"l4":                     model.Conf.Language(176),
		"l5":                     model.Conf.Language(177),
		"l6":                     model.Conf.Language(178),
		"l7":                     template.HTML(model.Conf.Language(184)),
		"l8":                     model.Conf.Language(95),
		"appearanceMode":         model.Conf.Appearance.Mode,
		"appearanceModeOS":       model.Conf.Appearance.ModeOS,
		"workspace":              filepath.Base(util.WorkspaceDir),
		"workspacePath":          util.WorkspaceDir,
		"keymapGeneralToggleWin": keymapHideWindow,
		"trayMenuLangs":          util.TrayMenuLangs[util.Lang],
		"workspaceDir":           util.WorkspaceDir,
	}
	buf := &bytes.Buffer{}
	if err = tpl.Execute(buf, model); nil != err {
		logging.LogErrorf("execute auth page failed: %s", err)
		c.Status(500)
		return
	}
	data = buf.Bytes()
	c.Data(http.StatusOK, "text/html; charset=utf-8", data)
}

func serveAssets(ginServer *gin.Engine) {
	ginServer.POST("/upload", model.CheckAuth, model.Upload)

	ginServer.GET("/assets/*path", model.CheckAuth, func(context *gin.Context) {
		requestPath := context.Param("path")
		relativePath := path.Join("assets", requestPath)
		p, err := model.GetAssetAbsPath(relativePath)
		if nil != err {
			context.Status(404)
			return
		}
		http.ServeFile(context.Writer, context.Request, p)
		return
	})
	ginServer.GET("/history/*path", model.CheckAuth, func(context *gin.Context) {
		p := filepath.Join(util.HistoryDir, context.Param("path"))
		http.ServeFile(context.Writer, context.Request, p)
		return
	})
}

所以问题的解决方法关键在于跳过鉴权过程，于是在本地利用 nginx 反代所有/assets/请求来实现

    server {
        listen       80;
        server_name  localhost;

		location /assets/ {
			alias D:/SiyuanData/data/assets/;
			expires 30d; # 设置缓存时间为30天
			access_log off; # 关闭访问日志
			add_header Cache-Control "public"; # 允许客户端和代理服务器缓存文件
			try_files $uri $uri/ =404; # 尝试直接返回请求的文件或目录，如果不存在则返回404错误
		}

        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   html;
        }
    }

然后在域名网关处利用 nginx 来实现 xxx.com 与 xxx.com/assets 访问不同端口

实际测试完美，问题解决 🤪