Census records for Luxembourg are online on FamilySearch.org. Choose Records; then Continental Europe; then Luxembourg.
1766 census: https://germanologyunlocked.com/sourcegermangenealogistsalmostalwaysmiss/
https://charteroakgenealogy.com/luxembourg/
In the Austrian era (the Netherlands, which included Luxembourg and present-day Belgium, were governed by the Austrian Empire), the cadastre imposed as a major administrative reform by Empress Maria Theresa abolished the privileges of the nobility and the clergy by listing the landed property of the privileged classes. This was the end of the Ancien Régime, well before the French Revolution confiscated the property of the Church.
The cadastre of Maria Theresa takes up the situation of the year 1766. This administrative reform laid the foundation for the modern state and constituted a property census to determine taxes (to this day, there is no administration similar to our "Registration" and "Cadastre" in Germany). The cadastral directory covers the territory of the Duchy of Luxembourg (including the future Belgian provinces: the documents relating to this are in the Archives of Arlon) and Lorraine (as a reminder: Étienne de Lorraine was the husband of Marie-Thérèse). The church administrations were a concession of Napoleon Bonaparte (Concordat of 1804 with the Holy See), in fact, it was a compensation for the confiscation of the ecclesiastical properties by the Revolution, as a pledge for the appointment of Napoleon I as emperor. It is not apparent whether the present government has any notion of canon law and the management of church property in the past.
See inventory: https://search.arch.be/en/?option=com_rab_findingaids&view=findingaid&format=pdf&eadid=BE-A0521_701871_701026_FRE
See FamilySearch catalog: https://www.familysearch.org/search/catalog/1184675?availability=Family%20History%20Library