So, I got this big xlsx sheet: last nonempty column is ARP (1160 columns). I imported it into Calc (4.4.7.2), the last visible column is AMJ (1024 columns remained), the rest got truncated.
Is this a bug or a known limitation of the xlsx import function / Calc itself?
Looks like it’s a bug, see Bug 50196 in the DocumentFoundation Bugzilla.
(Also some personal opinion: Bugzilla is a disaster, especially because it’s difficult to search efficiently. I searched for this bug before posting the question with Bugzilla’s built-in search and with Google too, and did not find the linked bug. Thanks for the Wikipedia article on LibreOffice Calc mentioning the 1024-column limitation and linking the bug in the references section.)