If you know of any FOSS, offline editors for Android which can do what silverbullet can, drop a link.

I use it and love it. Having the metadata (tags, dates, …) of your pages available to query and organize is awesome. I also love the tagged tasks feature.

I use nextcloud.export which comes with the snap (https://github.com/nextcloud-snap/nextcloud-snap/wiki/How-to-backup-your-instance), but the backup app looks nicer.