acreom is described as 'powerful knowledge base integrated with time management running on local .md files' and is an app in the Office & Productivity category. There are more than 100 alternatives to acreom for a variety of platforms, including Mac, Windows, Linux, Online / Web-based 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 acreom are Obsidian (Free Personal), Notion (Free Personal), Microsoft OneNote (Freemium) and Evernote (Freemium).
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.