It's probably the most well-known app for this, definitely most full-featured one. It's messy, and carries a bit of baggage of questionable design decisions, but that's a given for a program that's been in high-paced development for 15 years now. There are alternatives like Automate or MacroDroid, but they're simpler, less feature-full.

(EDIT: it may look like that some of the newer apps have similar feature sets, but the devil is in the details - Tasker tends to expose more parameters, give you more fine-grained control over any feature.)

(FWIW, Tasker has recently gained a sister project, Tasky, that tries to expose the same functionality using a much dumber^Wsimpler UI, geared towards more common scenarios and more casual users.)

> Open an app at a specific time, set volume based on location or time or Wifi, maybe react to more triggers from Apps, set display to monochrome after one hour of daily usage, stuff like that.

Most of those you can do without root. Recently, "Wireless Debugging" aka. ADB WiFi became a way to do some privileged activities without full root, and Tasker can use that too (caveat being, as I understand it, that technique only works when you're connected to a WiFi network).

Tasker may be a bit rough around the edges wrt. the UI, and the low-code model/language it exposes feels a lot like ol' PHP 4 in terms of stringly-typed data, but it works, and is well-established. Importantly, you can easily pair it with Termux, so if you prefer writing code over "GUI programming" with list views, you can use Tasker as an easy "event listener" layer, and just have your tasks fire Termux scripts.

You could also try Tasker

I also use Tasker to enable Do Not Disturb when using a set of applications: Kindle for ebooks, my meditation app, etc.