I set .csv files to be opened by ModernCSV by default last week (right-click the .csv file, select Get Info, in the Open With section, select a different app, click Change All, click the red x close button), and even after the Mac had restarted over the weekend, double-clicking .csv files started opening them in LibreOffice, and the default was changed. I have to change the default again now…
— double newline —
Is this intentional behavior by LibreOffice?
Looks like a Mac question to me; try this guide on a third party site for an alternative method How to Change a File Type's Default App in macOS - MacRumors
So you’re saying there’s nothing in LibreOffice that would ever re-take over ownership of .csv files, like after an update or a restart?