How does Worldcoin plan to solve for people in wealthier countries not wanting to scan their eyeballs (because the UBI isn't meaningful enough)?

Likely through a long tail of value props beyond the financial incentive 

For example, apps that require proof of personhood to use them, or voting schemes that require you to verify as a unique human 

Also early adoption of new technology often happens in developed countries b/c it is seen as high status

Building /bright-moments - minting onchain art IRL | /purple #15 | FID 129 #magikarp

Rome, Metropolitan City of Rome Capital, Italy

What historical technology have been adopted in developing countries and then become the norm and high status in developed countries?

Crypto, if you think about it. 

Adoption is happening in Brasil, Indonesia, Vietnam and other emerging markets. 

Sure, US cypherpunks used it first and European tech elites followed quickly but not sure that counts as adoption from a pure numbers POV.