Bolting on to this comment with some other neat things, as a fellow HASS enthusiast:
* Every single light in my house moves from dim/orange -> bright/bluer -> very dim/orange throughout the day (basically like an whole-home f.lux or Night Shift). Sadly still third party, but it's easy to use: Circadian Lighting component will find it
* I have "night" modes in all my rooms. This is usually a single bulb in lowest-brightness full red. You can barely see it during the day, but at night it makes bathroom trips a non-blinding affair
* I have 6+ speaker zones, on Raspberry Pis mostly. Snapcast runs the audio stream, but turning on/off a room mutes the speakers in it (walking into a room turns on the lights via motion detectors and music continues to follow, which is neat)
* I pipe a lot of text-to-speech messages. Some rooms won't play them if the room is off (outer stuff like my garage), but others always do (so I hear them). This is more custom now, and I even duck the playing music stream for the TTS portion. It can take in text, so I do things like have my automation say a bunch of things every morning (my age in days, some web-scraped snippets, etc)
* $10 power sensor is enough to know when your washer is finished. Power for awhile -> running state, no power after awhile in running state -> finished. This goes right into the text to speech system
* Every room has a 10-button remote (the very, very cheap zap remote kind). Most of the layout is the same--room on, room off, start music (or skip track if playing), stop music, full-bright lights, night lights. This still leaves a few for custom-to-the-room buttons, which I use
* Contact sensors on all openings to the house. I let me cats into the backyard during the day. Cat access via any configuration is still open, and sun is below X degrees? Text to speech
* Most of my logic is Node-RED (another comment here about that), which gives me a lot of flexibility. I have a global "house" mode, which I can set to guests or party to suppress most of my assumptions that I'm home alone
* Example of one of those: My setup knows if I'm using one of my two desk computers. If I am, and house is in "home" (alone) mode, I turn off all the other rooms in the house
I could go on--I went pretty deep when I first set up Home Assistant, but that was years ago now. Every now and then I do a major update or add functionality to smooth over something that's been bugging me
Once you hit some tipping point of soooo many things available as sensors or services in HASS, adding completely new functionality is a very incremental change