Generally, it's government or corporations like CITI who decide which app to use, not the public. They're not convinced by publicity campaigns but by beta trials like CITI is doing now with home tests.

Home tests are different as they are a retail sale. Seems like the trend is bundling "passports" with the tests. Most will use the app bundled, but QMCH makes the point their app can work with many different tests. When the time comes when there are competing low priced, easy to use home tests, then that will be time for a public advert campaign, not now. I see the passport becoming more important as the buying decision, and QMCH's unique "we don't share your data, you do" selling point will be a deciding factor.