I created an account but upon login it prompted me for a phone number for "additional security". After entering my cell, I got the message: "This phone number has already been used too many times for verification."
There seems to be no way around this whatsoever short of getting a new phone number. There's no way to contact a human being for support. Removing my cell # from other accounts (i.e. college, work) seems to have no effect.
A scary thought came to mind: If Google ever decides to kick me out of their system for my main account, I'm toast. I use it for everything.
How can I begin to practically "deGoogle" myself?
Regarding the Google Workspace, again there are alternatives, some self-hosted (but that's harder to do). One that comes to mind is the Proton suite.
Search engine is pretty easy to switch to (there is no network effect there). I really like Kagi, DuckDuckGo works well. For a non-US alternative (if you're into that) there is Qwant (Ecosia is European on the paper but I believe they use US servers).
For the mobile phone, you're pretty much screwed: it's Apple or Google. You can try to support projects that try to limit the power of Google over the OS. My personal favourite is GrapheneOS, but it only supports Pixel phones (hopefully that will change eventually). Linux on mobile is interesting, but IMO far behind AOSP (the open source part of Android).