Somnote is described as 'Record and save important information, brilliant ideas, and moments of everyday life easily and securely with SomNote' and is a Note-taking Tool in the Office & Productivity category. There are more than 100 alternatives to Somnote for a variety of platforms, including Windows, Mac, Online / Web-based, Android and iPhone. The best alternative is Joplin. It's not free, so if you're looking for a free alternative, you could try Standard Notes or Google Keep. Other great apps like Somnote are Microsoft OneNote (Freemium), Evernote (Freemium), Simplenote (Free, Open Source) and CherryTree (Free, Open Source).
Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, can be copied, tagged and modified either from the applications directly or from your own text editor.