I keep a spreadsheet in Nextcloud that I use regularly, and I prefer to just update it in my browser rather than download it locally.
Ever since NC updated to (25.0.2), the XLSX file just downloads on my computer when I click on it. I’ve tested this on macOS and Ubuntu with multiple browsers. Is there some sort of NC setting I’m missing?
do other office documents open normal in nextcloud office?
in settings → office does it show a green 
after you click save saying it is available or connected.
I’m not seeing that option in settings. None of the other office docs are opening including .odt. They’re all just downloading.
this indicated that you have not setup nextcloud office correctly.
https://docs.nextcloud.com/server/stable/admin_manual/office/index.html
you need to install or activate the office app aswell as a backend demo/build-in or standalone.
Thank you. I will take a look.