I couldn't find one that suited me, so I continued using TickTick. I tried very hard to like Vikunja, which is probably the closest alternative to TickTick, but the lack of an iPhone/iPad app, among a few other issues, drove me back. I didn't like using the right column to set task attributes. In my view, it requires too many clicks to set up a task with start/end times, effort levels, etc. This is especially painful on the phone. Another feature I missed in Vikunja was the drag-and-drop functionality that TickTick offers.

May I ask why would self-host simple to-do app? I'm just curious.

Joplin has to-do part. Nothing special (far from ticktick) but it can be self-hosted and has iphone app.