\documentclass{article} \usepackage{tabularray} \UseTblrLibrary{booktabs} \begin{document} \section{All good here} \begin{tblr}{lccr} \hline Alpha & Beta & Gamma & Delta \\ \hline Epsilon & Zeta & Eta & Theta \\ \hline Iota & Kappa & Lambda & Mu \\ \hline \end{tblr} \section{Pb here} \begin{tblr}{lccr} \hline Alpha & Beta & Gamma & Delta \tabularnewline \hline Epsilon & Zeta & Eta & Theta \tabularnewline \hline Iota & Kappa & Lambda & Mu \tabularnewline \hline \end{tblr} \end{document} From the post you gave, you can see it is just a workaround to use \tabularnewline in traditional tabular environment, because of the limitation of tabular. But tabularray is quite different in implementation from tabular and it doesn't have this limitation. Therefore you need not and should not use \tabularnewline any more in general.
In case you really need to use \tabularnewline, you can define \tabularnewline as \\ and use expand option in a tabularray table, see this question.
If you find problems in applying tabularray with other packages like acro or tcolorbox, you may ask some new questions for them.
incompatibleis probably the wrong term here. In the LaTeX kernel\tabularnewlineis only defined inside\@array, it is\relaxeverywhere else. You could register an issue about it ontabularrays github. BTW: you can see the definition via\typeout{\meaning\tabularnewline}inside a cell. Compare to what you get if you usetabularinstead oftblr.\typeout{\meaning... Merci !\tabularnewline? Can you show your use case?acroortcolorboxthat seem to prefer\tabularray. I will send 2 questions on this, sure you'll be able to help me :)