For context I've been using aerc as my email client for a while now, and was looking for something similar for calendars/tasks myself

I've tried:

• calcurse: fine but clunky, also a bit difficult to set up. The most mature option and probably the best one available, but I just couldn't get used to the interface
• calcure: similarly clunky interface, glitchy/blinking rendering to the point of being headache-inducing, lacking features (couldn't figure out how to look at all event attributes?)
• khal: limited in features (compared to calcurse) and slow when there are a lot of events (even when it's only 2-3 per day), also there are some rendering bugs sometimes. Probably the most intuitive and clean interface of all, and good scripting opportunities.
• gcalcli: only Google Calendar (I also need support for arbitrary CalDAV), didn't investigate further
• plann: no TUI as such, just CLI

A couple weeks ago I've decided to start writing my own. It's still very much a hacky WIP but I'll update in this thread if I ever decide to publish it. In the meantime, I hope one of the above works for you!

There's calcurse. It's in the arch repos.

I've tried a few options, but I've stuck with khal for years now.
It works smoothly [1], supports multiple calendars, syncs with vdirsyncer (details in its documentation), and provides both CLI and TUI interfaces that make events easy to see, edit, and manage.

The CLI interface is especially handy for integrating khal with other apps like neomutt and taskwarrior for example. For instance, I have a keybinding that lets me export calendar invites from neomutt directly into khal. There's also a list of tools (including one for khal) listed in the neomutt documentation if you're curious.

I use it to manage both my personal and professional calendars, syncing them bidirectionally with vdirsyncer. The only drawback I’ve encountered is that some commands can be a bit cumbersome—but I solved this by writing my own script to make khal’s commands more intuitive for my workflow. That flexibility could be seen as another strength of khal ;)

[1] That's my experience, but others here have reported it can be slow in some cases.

There's khal. It's fine, but can get pretty slow. pimsync for syncing.