Matisse Chapel: Chapelle du Rosaire de Vence

There is bus service. As of 2017 I was able to get a direct bus from Nice to Vence (not necessarily all the way to the chapel). There was a passing comment on the forum very recently to the effect that you now need to transfer. I think that would be either from one bus to another or from the tram to a bus. The intercity buses are run by Lignes d'Azur: https://www.lignesdazur.com/en/nos-lignes That might leave you with a bit of a walk to the Chapel; Google Maps indicates you can get closer by changing buses again.

The historic center of Vence is a very worthwhile stop. It doesn't get a great deal of tourist traffic. If you zoom in on the map you should be able to identify it easily; it's the nearly circular area around the Cathedral.

While you're going that way, if you have extra time you might want also to see the Galerie Maeght in St-Paul-de-Vence and the village of St-Paul-de-Vence itself. The latter is tiny, handsome and overrun with tourists, few of whom care about the Galerie Maeght, so the Museum itself shouldn't be crowded--or at least it wasn't for me in May 2017.

Yes, the direct bus I believe is eliminated or largely cut back. You have to transfer from the tram or train (or bus) to get to Vence. From the bus stop you can walk (slightly uphill). Unfortunately it is a walk to the old town as well, but that is closer to the chapel but a side trip from the main route to the Chapel. Note they close at lunch for two hours . The Chapel is small but also includes some religious garb made using the same technique, btw, except with fabric.

It is so unfortunate for you that the Matisse Musee central collection is on loan until the end of May (and that exhibition in Japan is specially focused on the cutout pieces -- I can understand the cultural crossover interest there). There are numerous examples of his cutout work, including a very large scale piece in the central hall

As others have noted, you'll need to take a train and then a regional bus. The chapel is an uphill walk from the Vence central bus stop, which is at a roundabout. At the roundabout, there is a city bus that goes past the chapel, I think it's #47. Be sure to check the hours of the chapel first. They are sporadic, and there are several day-long closures. But it's worth it for a wonderfully spiritual experience.

Thank you for your help. I hope to be able to see this beautiful chapel!