Huawei has 22% market share in China which has its own ecosystem, so apps can be converted. Even for Xiaomi and BBK it will make sense to have few China only Harmony phones to hedge against any action by US against them.

Countries like Iran, Russia can be next target for obvious reasons.

In SEA likes of Grab and Gojek can be financially motivated to create apps. If they get a 4-10% marketshare it will make sense for Meta to port its apps to protect its position.

YouTube will be a blocker as Google has strong reason to not support any alternative platform even if it will make sense for the App. Same happened for Win Phone earlier.