See this linked article.
https://www.flightglobal.com/news/articles/a350-900ulr-will-have-inactive-forward-freight-hold-449495/
Not only will pax capacity be reduced to 173 seats (80J / 93PE) on a plane that ordinarily holds 315 in the regular -900 version, but the forward cargo compartment will also be blocked off. So no cargo revenue and necessarily very high pax ticket prices. Other than for some very, very high premium-demand niche markets, it seems hard to imagine that it will have many takers. Looks just like the A340-500 all over again.