And while I have a little bit of time, here are some other links for 2019:

The Water Management System of Augsburg: https://wassersystem-augsburg.de/en/start

The Prosecco Hills of Conegliano and Valdobbiadene: https://www.prosecco.it/en/area-of-origin/visit-conegliano-valdobbiadene/

The Historic Centre of Sheki with the Khan's Palace: https://azerbaijan.travel/en/place/121-sheki-khans-palace (appears to be from Azerbaijan's official tourism bureau, but lacks details such as opening hours)

Risco Caido and the Sacred Mountains of Gran Canaria Cultural Landscape: https://riscocaido.grancanaria.com/inicio

Jodrell Bank Observatory: https://www.jodrellbank.net/

The 20th Century Architecture of Frank Lloyd Wright: https://franklloydwright.org/ (includes links to each of the eight inscribed sites on the UNESCO announcement page)

Thanks a lot, Colvin. I will be adding them.

I've added a few more from 2019, seems we have forgotten to do the excercise after last year's inscriptions.
Can use help though with finding official websites for the following:
- Ancient ferrous metallurgy sites
- Babylon
- Bagan (lots of commercial websites around but none really fit the bill)
- Hyrcanian Forests
- Jaipur City (there's a site from the ASI, but little info)
- Migratory Bird Sanctuaries
- Ombilin Coal Mining
- Plain of Jars

I don't think there is one globally for the bird sanctuaries. Here is one for the Red-Crowned Crane sanctuary:
http://www.ycwetlands.com/en

No problem. BTW, this page on the Frank Lloyd Wright foundation site has links to the remaining sites, such as the Robie House and Jacobs house: https://franklloydwright.org/eight-frank-lloyd-wright-sites-inscribed-on-unesco-world-heritage-list/

Here's an official link for Jaipur: http://www.tourism.rajasthan.gov.in/jaipur.html

Still, it lacks ticketing information (why make things easy?), so this site may be complementary: http://museumsrajasthan.gov.in/

This looks like an official tourism site from Iran, but while they have a page on the Hyrcanian Forests, it doesn't have much useful information: https://www.visitiran.ir/attraction/caspian-hyrcanian-forests

When writing my reviews for the Japanese WHS, I noticed that we don't have the official websites for the individual temples in Kyoto and Nara. Here they are:

Ancient Kyoto
Kamigamo shrine http://www.kamigamojinja.jp/english/
Shimogamo Shrine http://www.shimogamo-jinja.or.jp/english/
To-ji https://toji.or.jp/en/index.html
Kiyomizu-dera https://kiyomizudera.or.jp/en/
Enryaku-ji http://www.hieizan.or.jp/ (in Japanese)
Daigo-ji http://www.daigoji.or.jp/index_e.html
Ninna-ji http://www.ninnaji.jp/en/
Byodo-in https://www.byodoin.or.jp/en/
Ujigami-jinja https://www.discoverkyoto.com/places-go/ujigami-jinja/
Kozan-ji http://www.kosanji.com/ (in Japanese)
Saiho-ji http://saihoji-kokedera.com/en/about.html
Tenryu-ji http://www.tenryuji.com/en/
Kinkaku-ji https://www.shokoku-ji.jp/en/kinkakuji/
Ginkaku-ji https://www.shokoku-ji.jp/en/ginkakuji/
Ryoan-ji http://www.ryoanji.jp/smph/eng/
Hongan-ji http://www.hongwanji.or.jp/english/
Nijo-jo http://nijo-jocastle.city.kyoto.lg.jp/?lang=en

Ancient Nara
Tôdai-ji http://www.todaiji.or.jp/english/index.html
Kôfuku-ji http://www.kohfukuji.com/english.html
Kasuga-Taisha http://www.kasugataisha.or.jp/about/index_en.html
Gango-ji http://www.gangoji.or.jp/tera/eng/top.htm
Yakushi-ji http://www.nara-yakushiji.com/en
Toshodai-ji http://www.toshodaiji.jp/english/index.html
Nara Palace Site http://www.nabunken.go.jp/heijo/museum/index.html
Kasugayama Primeval Forest https://www.visitnara.jp/lists-and-stories/story/hiking-the-forest-of-the-gods/

And the official website for Horyu-ji and Hokki-ji
http://www.horyuji.or.jp/en/

Great work! As are those reviews, I enjoy reading them.

Thanks. There will be a few more on Japan in the next days.

Doing some research on various sites and I noticed that the official websites for Armenia's WHS seem to be down, and the domain has expired. I managed to find this official government site, which has pages for each of the three locations included, but of course no opening hours/ticket info etc.

https://armenia.travel/en/armenia/unesco-heritage

I found this site useful when I planned my trip to Armenia many years ago, and it seems to be still working: http://www.armenianheritage.org/en/

Thanks Sjobe and Joel, I have added them both.

I'd like to report that the truly official website for Leonardo's Last Supper is

https://musei.lombardia.beniculturali.it/musei/museo-del-cenacolo-vinciano/

i.e. the dedicated page in the Lombard section of the site of the ministry for cultural heritage and tourism. It sketches all details, even if only the Italian version has a working link to VIVATICKET (why?!).

The one provided now (http://legraziemilano.it/) has its link to the Last Supper dead at the moment, but besides that, it does not belong to those who manage the Last Supper's museum*. The church and the museum are two completely separate entities.

I hope this information will help some future visitor, because unfortunately the web brims with para-sites which have all the look of officiality but offer overpriced, guided tours and give a misleading impression of the visit. I don't understand why they rank so high in search engines with respect to the official one.

*Absurd note: if you go look at the section Omelie domenicali ('Sunday sermons'), you will find the Lorem ipsum. Well, this gives a measure of how well the site is maintained... Dio santo (= my God).

I don't think this is a fraud or a para-site - the web address is owned by the Frati Domenicani in Italy and it is the official site for the church/convent. The only issue indeed is that "The Last Supper is a State Museum and therefore is not under the direction of the Dominican Friars."

I've added your suggestion as well, so now we have 1 for the Church/Convent and 1 for the Last Supper "museum".