The closest free alternative to Trello would be Planka, IMHO. It works really well (rock stable, quick, painless), is pretty and doesn't need much resources. The only thing I miss (which Trello also lacks, btw) is the ability to have subtasks in the way Jira allows them; for this, Plane or Leantime might be good candidates (I haven't used either of them yet, though).

Nextcloud Deck is a really good choice and I use it, but I also know Vikunja is great

Maybe https://vikunja.io/ suits your needs.

new kid in town: https://plane.so

I use Nextcloud Deck now, but before that, I used Wekan.

Wekan was great and has more features, but Deck does all I need and I'm already running Nextcloud anyway.

Not sure about Docker integration but I use Asana for this sort of thing.

I have Kanboard up in a Docker container.

Not the most flashy or modern but lightweight and gets the job done. Good if you want something very easy to spin up in Docker.

I use Obsidian with the Kanban plugin to organize my personal projects, and sticky notes on my wall for other things.

I'm happily using Nextcloud Deck. If you're already running Nextcloud, it's trivial to set up. But I've never used Trello, so I don't know how they compare; I would bet Trello has more features.

I use Kanboard.

I use TickTick which is perfect for my needs. Not self-hosted but it is free.

Azure DevOps free tier is probably enough. You can also host your own private repos there.

There are a number of open source web apps that are based around "kan ban" which is similar to Trello in approach. A few are:

• Kanboard https://kanboard.org/
• WeKan https://wekan.github.io/
• Taiga https://taiga.io/#Features

There are more out there if you search for "open source kanban" or "open source kan board".

I like the appearance of https://taiga.io/ but I haven't gotten around to try hosting it myself

Try Notion. It is great for personal stuff, highly customizable. They have also added a set of project management tools recently.