I use it to manage my documents, backup my photos from my phone to my server and access all my files from any other device. Basically Nextcloud is my replacement for OneDrive.
Additionally, I have used it in the past to collaborate on various group projects which require documents. For example, I had to make a presentation with some other people and I could create a PowerPoint in Nextcloud, send a share link to others and then we could edit the PowerPoint in realtime with Nextcloud + Collabora, which is pretty cool. It's the only FOSS alternative (at least as far as I'm aware of) that can compete with Microsoft 365 / Google Workspaces.
Tip: if you have an Android TV, you can install SmartTube as an alternative, privacy-friendly YouTube client. It has no ads and sponsorblock integration