Sounds like you’re left with almost no modern conveniences or technology.
You are right, I forgot one exception. I do use a Google Phone because these have the best support for alternative operating systems. I replaced the Stock Android which is filled with Google spyware with GrapheneOS, an entirely open-source version of Android which makes many privacy and security improvements and gets rid of any Google services. Watch this video to learn more about it: piped.smnz.de/watch?v=yTeAFoQnQPo
On my laptops/computers, I exclusively use Linux. I refuse to touch any bloated, ad- and spyware-infested Windows computer. Yes, even at work. As a DevSecOps and Senior Linux engineer, I am free to choose whatever operating system I want. Free and open-source software is the way to go.
I use Firefox (LibreWolf, a better version of Firefox to be percise) with DuckDuckGo as my search engine, I watch YouTube videos through Piped, I use Signal as my messenger, I use Proton for Email, I self-host Nextcloud for my files, contacts, calenders, etc.
For entertainment, I simply pirate the content which gives me much more freedom compared to shitty streaming services like Netflix. That way, I also don’t have to give these shitty corporations any money. I use the open-source Jellyfin media server to consume content from my media library. I do the same thing using Navidrome for my music.
Regarding Social Media, Lemmy is probably the only thing I use. I don’t need Facebook, Instagram, Twitter or TikTok.
And the list goes on and on. I could write an entire book about avoiding proprietary software and shitty corporations.
ensure you are truly not using any of these companies or their subsidiaries
I do everything in my control to avoid it. I can’t 100% guarantee it, but that’s also not my goal. Not giving them my money or my data is enough for me.
Or even if a mom and pop shop down the street is using technologies, software, or appliances from one of these companies to run their local business…
All of those shitty Big Tech companies including Apple, Google, Facebook, Amazon, Microsoft, Oracle and many others, all corporate Social Media platforms (including Reddit of course, fuck Spez), those shitty Hollywood media corporations, CDNs like Cloudflare or Akamai, Tesla and everything related to Elon Musk, Starbucks, basically all fast food chains, every Chinese or Russian company, every Israeli company, The Coca-Cola Company, PepsiCo, Nestle and many others. I also try to stay away from PayPal, banks and insurance companies as much as possible, they are criminals.
We shouldn’t just focus on shitty companies. Foundations like the Bill & Melinda Gates Foundation are basically tax-exempt billionaire investment funds in disguise. This is a great video about the lies of billionaire philanthropy: https://youtube.com/watch?v=OH4uh8cHuto
GitLab is mean for large enterprise environments. It’s overkill for most users. Gogs/Gitea/Forgejo focus on simplicity. These are also pretty easy to self-host.