I've been in that situation 3 times, I choose React Native and Flutter each once. I was forced to use Ionic. I would NEVER use Ionic again, terrible experience and very difficult to get decent quality/performance. I like Flutter's technology much more. I like that it is natively compiled. I dislike that it has it's own UI toolkit. React Native with TypeScript is a highly productive environment but I LOATHED the developer experience and any code that had performance goals was way harder to be successful with, not impossible but the threading model that RN imposes (it doesn't really thread at all) was hard to make the UI snappy and crisp as it should be. I've played with Xamarin also since I was a .net dev for 10+ years (I'm old in the industry 25 years now) and the developer experience was actually pretty good but the compile times and the UI performance were not. Though that was not a production level app and I might have been able to make it work.

tldr; If I HAD to do cross platform I'd use the following logic to choice one: If I have a team of react JS/TS devs: React Native else if I have a .net team: Xaramin else: Flutter

Then I'd apply for a job writing native apps in Swift/Kotlin and run away ;)