This is Parliament's comprehensive website on the major constitutional reform that took effect on July 1, 2023. As shown in the timeline, the reform had been in progress since 2009.
https://www.chd.lu/fr/RevisionsConstitution
The new and older versions of the Constitution can be found
on Legilux.
I don't know the exact ins and oust but it seems that a lot of other things have changed not just the constitution referring to the Grand Duke and monarchy. It seems like, as you can imagine given the old constitution was 175 years old, it didn't reflect modern Luxembourg. One example - the annual allowance for the Grand Duke and heir were set out in the old Luxembourg Franc currency - no longer used and replaced by the Euro.
While the constitution dates from 1868, it had already been amended numerous times. But the recent reform was much more comprehensive than most previous amendments.
The reform's effects on the grand-ducal finances went further than deleting the reference to francs.
Under the previous version of the Constitution, the amount of the civil list was only modifiable at the beginning of each reign. In addition to the civil list, the Sovereign House could also be allocated money in each year's parliamentary budget to cover their representation costs:
Art. 43.
(Révision du 6 mai 1948)
«La liste civile est fixée à trois cent mille francs-or par an.
Elle peut être changée par la loi au commencement de chaque règne. La loi budgétaire peut allouer chaque année à la Maison Souveraine les sommes nécessaires pour couvrir les frais de représentation. »
Now, after the reform, there is no longer a single civil list, but separate dotations for the Grand Duke, the abdicated Grand Duke, the Hereditary Grand Duke, the Regent and the Lieutenant-Representative. The amount of the dotations can be modified every year, not only at the start of a new reign.
Art. 54.
Le Grand-Duc, l’ancien Chef de l’État, le Grand-Duc Héritier, le Régent et le Lieutenant-Représentant touchent sur le budget de l’État une dotation annuelle, dont les éléments et le montant sont fixés par la loi.
The amounts of the dotations for this first year were already voted through in June.
https://today.rtl.lu/news/luxembourg/a/2071734.html
It looks to me like its been in large part a "cleaning up" to allow the constitution to reflect the Grand Duchy of today.
Exactly; one of the main motives for the constitutional reform was to make the text of the constitution correspond to the way in which the grand duchy already operates.
Most of the changes regarding the monarchy seem to have already been in place (change to succession laws etc).
I would agree that changes such as stating that the Grand Duke exercises his powers in conjunction with the government, and that his constitutional functions are obligations and not prerogatives, were already in place in reality.
But I'm not sure that can be said of the succession laws, as I would say they were comprehensively revised by the new reforms.
https://www.theroyalforums.com/forums/f69/luxembourg-succession-and-titles-33317-9.html#post2561196