Ask HN: Should I bother with UI Testing or focus on more API testing?

Hi all, LTL, FTP, looking for some advice on testing strategy. Thanks for reading.

Some context: I have some time carved out within the next few weeks to deal with tech debt and to improve the automated testing around our upcoming SaaS product. It is a React based Frontend consuming a REST API in Go.

I pushed for and managed to introduce some UI testing. I had used Selenium in the past, however opted for Puppeteer instead this time round. Me and another engineer managed to write a number of use case tests, however we found it very clunky to work with and it tended to be quite flaky.

I recently remembered reading an Uncle Bob book where he recommends testing ends at an API level, and to not test UI. Opinions of Uncle Bob aside, should I bother with pushing through and testing our UI better (as we have had some avoidable issues when the backend has undocumented breaking changes since its still a bit in flux), or stick to battering the backend as much as possible and leave the front end to manual user testing?