I'm trying to decide how concerned to be about Google's upcoming #Android "lockdown." In 2015, I switched from iPhone to Google Nexus, and I have since really liked the Pixel line. I've used Google Fi for my cell phone provider for nearly 11 years and have no complaints. I only use apps from the Play Store and see little need for more. (I would like a Gutenberg e-book reader like Myne, however, but have no shortage of reading material.) Yes, Google sells all kinds of information about me, but...

...as long as I get inexpensive cell phone service and a good assortment of the apps I need or want, what other things should I consider?

I'm studying the matter and keeping my eye on f-droid.org and nexphone.com/.

Informed opinions and feedback are appreciated. What steps should I take prior to "Android lockdown" and why?

@RABid many people have been very concerned about this, much bacause the lack of information from Google.
But its clear now. What is happening is that in order to install apps from other sources than Google Play, you need to go into the settings, enable developer mode and toggle a switch. After you have done you have to wait 24 hours before you can install apps from other sources.
You only need to do this once. (Maybe also only once per Google account, not once after every time you have installed a new phone. Though that part I'm not sure about).