It arguably has some downsides compared to Keep, however it suits my needs and as a plus it supports markdown formatting.
Additionally it's open source, so you might get some insights into which thoughts went into it, which might help when designing your own solution.
It also only supports text notes, so if you use drawings, etc in Keep a lot that might be a problem.
What I really like about it though is its simplicity and that I can easily run my own instance (of Nextcloud which I use anyways).
It arguably has some downsides compared to Keep, however it suits my needs and as a plus it supports markdown formatting.
Additionally it's open source, so you might get some insights into which thoughts went into it, which might help when designing your own solution.