They're using feature phones which are 100% proprietary and actively fight anyone from sideloading any app at all because they're uncomfortable with Android's ecosystem, which by comparison lets you install pretty much whatever you want if you just enable developer mode on the device?
No. People who choose feature phones do so because they don't want to deal with apps at all on their mobile device. Not iOS apps, not Android apps, not Debian apps, not Ubuntu apps, not Symbian apps, nothing. They're wanting a phone that's just a phone, even more of an appliance than an iPhone. They probably wouldn't care about the phone running Debian at all, and they absolutely won't care about running GCC to compile their own apps on their phones.
No. People who choose feature phones do so because they don't want to deal with apps at all on their mobile device. Not iOS apps, not Android apps, not Debian apps, not Ubuntu apps, not Symbian apps, nothing. They're wanting a phone that's just a phone, even more of an appliance than an iPhone. They probably wouldn't care about the phone running Debian at all, and they absolutely won't care about running GCC to compile their own apps on their phones.