Regulators really need to crack down on Google and Apple using “security” as an excuse to evade their anti-monopoly court judgements.
If this works the same as Advanced Protection Program though, you’ll be able to sideload APKs for initial app installs via ADB, and then any alternative app stores you sideload with ADB will be able to update themselves and those apps on-device from there on out. Still annoying, but not the end of the world.