If they're "just" using Signal, they're likely "just" using stock Android if there isn't a policy requiring iPhones in lockdown mode. It's a very good question as to whether such a policy exists.

At this point it wouldn’t surprise me if they were using free Android phones they won in a raffle set up by foreign intelligence agents

Which do you think is more likely to be under foreign control and why? Bearing in mind that iPhones are made in China.

stock iPhones run 100% Apple software, afaik. from drivers to the shell it's one company. the hardware is one series of models by one company.

each Android vendor has a completely random fork of AOSP with who knows what kernel patches, out-of-tree drivers, unremovable apps and customizations. you're trusting an enchilada of your mobile carrier, Google, Samsung/OnePlus/whoever, plus all their vendors.

Android can be highly secure. the NSA's Fishbowl project used vanilla AOSP + SELinux + IPSec on closely scrutinized hardware to make a phone that can be used for Secret text messages. the cheap prepaid phone you buy at T-Mobile is not that.

> stock iPhones run 100% Apple software, afaik. from drivers to the shell it's one company. the hardware is one series of models by one company.

> each Android vendor has a completely random fork of AOSP with who knows what kernel patches, out-of-tree drivers, unremovable apps and customizations. you're trusting an enchilada of your mobile carrier, Google, Samsung/OnePlus/whoever, plus all their vendors.

That cuts both ways though. Any exploit for iPhone works on a lot of high value targets. An exploit for one android phone may well not apply to another. If we're talking about state actors, well, probably both are compromised, but the iPhone would be the priority IMO.