I just can't imagine scenario where it's cheaper to use something like Flutter and port, test, debug and maintain it in operating systems and devices myself or find consults to do it to me.
I'm an entrepreneur with 6 guys working for me. 4 of them write embedded software, 1 uses Qt. I pay for Qt because cost/value is right. I don't develop any more software than I have to. I get a product, I can buy consulting with reasonable price.