you need a bit of tech savvy for this, but
There is a program called homebridge,
It's a home kit server, that allows non-homekit devices to become available for control in the home app and with siri.
There are tons of plug ins to control various things.
It does needs a computer running full time, but even a raspberry pi is powerful enough for most users (cameras can be a bit taxing for the Pi) and since you have an appleTV, you will also have access to all your devices from outside your home
I've got a plugin that talks directly to my TV, so i've got a device in the home app that's my TV power, and can turn it on and off with siri, or you could set an automation for when you return home.
I also have an additional device for each of the inputs and apps that i use on the TV. So I can say "turn on HDMI 3" and the TV will power on if needed, and switch to that input. or "Turn on Netflix" and The TV will launch netflix.
The amount of control you have will vary greatly depending on the model of TV you have.
There are also plugins to talk directly to the appleTV,
they can be configured to send multiple commands, but due to the limited amount of control the aTV has, if you want to launch a specific app, it can be a bit tricky, since you can only simulate hitting the buttons on the remote.
so turning on a specific device in the home app would send the appleTV "home - right - right -right - down - enter"
or you could just have a device that sends the home button, which should be enough to wake the aTV and your TV.
homebridge
Homebridge AppleTV
and to see if you can talk directly to your TV just google "Homebridge and the make of your TV'