I am also on the hunt for a good self hosted journal for life journaling (not note taking like some other links in other comments). Here's what I am trying to replace:

I've been using DayOne without subscribing. I've had a lot of ups and downs with DayOne over the years, but I've finally found a way to use it with the free plan that I'm happy with, that kind of fits into a self hosted setup. I journal on my phone, and also in my laptop. I love that it captures location, weather, music, step count, and activity. After a month or so, I export the journal entries as json, and put them into a private hosted view and search interface that I'm in the process of writing in Python.

The DayOne journal data does not need to be synchronized to the cloud, and can even be encrypted by you, but who knows how much of your metadata is sent to them.

This setup is far from ideal because it's not entirely private (metadata is probably leaking to the company), but it does have solid data liberation, is free (as in beer), can be encrypted, and the format is just json so it's easily inspectable and transformable. It's been working fine for me for several years (I actually have over a decade of DayOne journal history). It's kludgy and not turnkey, so definitely not for everybody.

Side note for anybody who is using DayOne: I highly recommend making sure your backups are working, and saving a copy of the backup periodically. I store my exported entries in git and over the years have observed lots of instances of corrupt data due to sync problems with their sync server, which is another reason I want to move to self hosted.