https://faq.whatsapp.com/686469079565350/?helpref=hc_fnav
I didn't end up going through with it through since there was no way to take a Signal backup created in Android and restore it to IOS.
As I pointed out in the post, this was pretty much the dealbreaker for me. I had initially set up the iPhone without all of my accounts, just for development, but had gradually carried over my accounts and the apps I need to use. And then I find out that I’d basically need to wipe all of the progress and start over, just because the data move can’t be initiated with an already set up phone (which probably made developing the app easier, but at the same time limits its usefulness).