uglyurls support is configured as map[string]bool according to the following link

• hugo/config/allconfig/allconfig.go

  Lines 335 to 344 in 9b63552

  	isUglyURL := func(section string) bool {
  	switch v := c.UglyURLs.(type) {
  	case bool:
  	return v
  	case map[string]bool:
  	return v[section]
  	default:
  	return false
  	}
  	}

• hugo/config/allconfig/alldecoders.go

  Lines 413 to 428 in 9b63552

  	"uglyurls": {
  	key: "uglyurls",
  	decode: func(d decodeWeight, p decodeConfig) error {
  	v := p.p.Get(d.key)
  	switch vv := v.(type) {
  	case bool:
  	p.c.UglyURLs = vv
  	case string:
  	p.c.UglyURLs = vv == "true"
  	default:
  	p.c.UglyURLs = cast.ToStringMapBool(v)
  	}
  	return nil
  	},
  	internalOrDeprecated: true,
  	},

but not work

because v is maps.Params[_merge:none post:true] in p.c.UglyURLs = cast.ToStringMapBool(v), none should be clean