So, other than being CLI, Taskwarrior fits the bill very nicely. I tend to fall on/off the wagon for task management, and taskwarrior outlasted all of them, and is probably the first I turn to next time around.

The good news is that other people have created tools to interface with it, here, including one web-based interface. I can't speak to the quality of these though.

Trello might fit your needs. More Kanban but still a common project management flow which is the same as a ticket in practice

I would recommend Vikunja. It is open source and easy to run in a docker container.

It is pretty flexible and supports email notifications. Looks like there is an app on the way too, though it works fine for me through the web interface.

Trello or Jira would work here. Both are free but only web-based on Linux. You can assign priorities, keep track of tasks already completed, comment on tasks to keep track of where you are in each task.

Textfiles/Markdownfiles

I use the following filestructure:

tasks/
     done/
     lowprio/
     blocked/
     task1.txt
     in the file:
          - [ ] subtask1
          - [x] subtask2
          ... other subtasks, x marks them as done
          other info
     task2.txt
     task3.txt

whenever I get a new task I create a new txt file, when a task is completed I move it to the done directory.

As tool I use pycharm because I already use it for programming, if you most of the time you already have something open that handles textfiles I would use this, otherwise I would recommend obsidian.

Pros:

• low complexity
• lots of choices for tools, you can use anything that handles textfiles
• easy to search, just use textsearch to search all files
• low clutter, in jira for example there are often a lot of fields I dont care about
• fast
• for tagging just use #work and then search for it
• you have file timestamps for modified date
• easy to put into git

Cons

• what was really nice in onenote is that it had the win+n shortcut for new notes, you can create this for textfiles but that is at least some effort
• no email integration, in outlook 2016 you can flag emails and then you have a list with emails where you have to do something

General thing I learned about managing tasks

• you want a single place where all your tasks are, else it is easy to overlook something you have to do( I often forgot about emails because I didnt create a task for each email where i have to do something)
• you want creating/ editing/ viewing tasks as low overhead as it can be so you actually do it
• dont overthink what you write, often email_from_x.txt with no content is enough, the more you do it the more you know how much exactly you have to write, also it only has to be understandable for you, so dont worry about grammar, again you want low overhead of creating the task
• you only want max 5 tasks or so active at a time, so move the remainder into lowprio and if you need more get them from there, the problem with too many tasks there is you spend too much time deciding which task to do instead of doing the task
• in meetings/phonecalls write down what you have to do with a few bulletpoints and at the end possibly repeat them and ask if you missed anything
• sometimes the task is small enough to just do it without recording it.
• when interrupted it can be useful to note down what you are currently doing so you can easier continue later
• if you have to undo something later, e.g. you commented something out in the code, it can be helpful to make this a subtask so you dont forget it.

If you are ok self hosting something, Taiga is a self-hosted jira replacement.

I'm the Emacs guy, so I'm going to suggest Emacs, specifically the org-mode and org-roam packages. Here's the org-mode website detailing how it works, and here's a pretty good video of one guy's system. It's all text-based so it can be used in a GUI or CLI setting (though I almost exclusively use it in GUI mode just for convenience), it's all local, it's highly extensible, and there are dozens of user-created extensions and premade setups out there.

Emacs on the whole has a steep learning curve, but it's not at all impossible to learn. Personally I got the basics down in less than a week when I started, and there are dozens of packages that make it more modern. If you've a Vim user already then the evil-mode package adds Vim keybindings into Emacs, for instance.

I'm going to recommend Joplin. You can run the client locally, and create either pages or tasks. Both are created as markdown files. It supports tagging out of the box.

I run the sync server on my local network (homelab/home server). Regardless of if you use their server or your own, you can do end-to-end encryption of pages.

I set up a "sticky note" of sorts that displays contents of a Joplin note on my desktop, pulled from the sync server API. (This is on Windows but I'm sure there's a way for whatever Linux DE you're using if you're running Linux client side.)

This is my solution after much deliberation. Flexibility is the reason I did this - I can put whatever I want in a note, including links.

If you want more structure, consider running a git server. You can create a tasks-only repo in something like forgejo/gitea so you just use the issue tracker.

Have you considered CalDAV reminders? It is very basic and not at all like Jira-like solutions, but very easy to set up and share across devices and platforms. It seems to tick most of your requirements, so maybe just good enough to use? I run a davical server, but there’s probably more modern options available.

I use kanboard for keeping track of my tasks. Simple to use, super simple to run on a local server.