I've used my past several Android phones without signing into a Google account or using gapps. I pick something with LineageOS support (usually OnePlus stuff) and get it from eBay, update to latest stock firmware (gets newer baseband and such) then flash LineageOS over it and get my apps from F-Droid.
These, “just change the firmware” comments are silly. I should get basic phone functionality from my phone out of the box with exactly ZERO effort.
I can use an iPhone without an Apple account. I cannot use an Android phone without a Google account unless they changed that in the last few years.
Both Android and iphones require an account to download apps I believe. Am I mistaken here? Other than that they can be used in the same way without accounts. In fact, with Android an email account suffices and giving your phone number is "opt-in". Apple forces you to give your phone number to create an account last time I checked. Also no F-droid on iphones? But the iphone is the better "phone" experience because there is less bloat and UI nagging.
Android does not require an account to download apps, as grandparent pointed out.
I haven't "signed in" to Android phone in 10 years.
You absolutely can use Android without a Google account. I have a device like that currently. You won't get the play store and some other features, but I believe that is also true of Apple (at least was of it isn't any more)
The other aspect with setting up third party firmware as a general "don't like the stock OS? then do this" option for many is besides the big headline limitations like safetynet/attestation, it also either involves a benevolent third party setting up and maintaining builds for your device (hope you bought a popular model) and any changes match what you want, or individuals doing so themselves
You can, but you don't get access to the app store.