There are a few ways you could do this. The easiest way to create something like a traditional diary entry on Discourse is to send a PM to yourself:
Another approach for your use case would be to create a “grow-logs” category. It could be a place where people post updates about what they’re doing, what equipment they’re using, etc.
I’m interested in the diary idea because it could be solved in a similar way to what would be required to use Discourse as a publishing platform - for example, to use Discourse to create a small version of Substack, or to have a Discourse site that allows multiple people to publish their Obsidian Notes.
A possible solution would be to create a Discourse category and group for each publisher:
A benefit of this approach is that it allows you to control how users can interact with the category. In the example below, only members of the “simon” group (me), can create new topics in the category. Everyone else can see the category’s topics and reply to them.
Note that there are good reasons for not creating a group and category for every user on your site. In the past, having a huge number of categories on a Discourse site caused a performance issue. I think that’s been solved though. Having a huge number of groups and categories on a site will cause a UX issue, at least for site staff. Unless something has changed, hosted Discourse sites can only create a limited (but reasonable) number of categories.
That said, I think the category/group approach would be a good solution for sites with 10-20 separate publishers, diary creators, note takers, etc.