Hey,
As someone that absolutely loves smart home / IoT, is a developer, builds my own stuff. I'm not gonna sugar coat it.
Smart vacuums with SSH backdoors that sell maps of your house to advertisers, devices where functionality you pay for gets a firmware update that removes that functionality, devices that get abandoned by the manufacturer leaving you with expensive paperweights - these are all common everyday things. For normal, non technical consumers, Smart home is an absolute minefield. To achieve a smart home that doesn't essentially fuck you over as a consumer, it is difficult, you will need to invest significant amounts of time and money, but, it is technically possible. This is what I do.
Other posters have recommended Home Assistant, it's great as a hub. You can set it up on a computer you control, and it generally respects your privacy. That said, if you don't have experience with Linux, networking, etc, it is easy to make a mistake and open up yourself up to "hackers and general lowlifes". You need to read and understand what you're doing. I'd read the official manuals for things, folks on YouTube often give incorrect or bad advice, because ultimately everybody makes mistakes, this is complicated stuff. You can make home assistant pretty secure by using a VPN like wireguard for ingress, can't hack it if you can't connect to it.
Device selection is going to be hard. Lots of devices only operate via the cloud anyway, one easy solution is to dive straight into Zigbee and/or Zwave devices, these devices communicate via radio and pretty much can't violate your privacy as they don't have an internet connection. For WiFi devices, it's a lot more complicated, devices generally don't tell you upfront and will require reverse engineering to figure out how they work. Lots of stuff may say they are local only but then require the manufacturers app and an account to setup. There are some that are designed well (Shelly is a great example), but most sadly are not. As a blanket statement I would say avoid anything WiFi or Ethernet unless you are confident they are local only, and you have a networking setup that allows you to firewall their internet access. Sometimes devices are significantly more expensive, for example a ring doorbell is only £50, while my Dahua VTO2202F-P is more like £150, but at least it works fully locally.
Amusingly, I don't much care about the privacy aspect, I just want my stuff to work when my internet is down, and I don't want to build my smart home around devices that the manufacturer will eventually drop support for. People will ridicule you for it and tell you to go buy an Amazon echo, so no doubt enjoy that too.
Good luck, and if you have questions, feel free to ask.
Dreame, Here you go 29:41.