We also use flutter, and have extensive native code that needs to be compiled for each platform/abi. What you describe is similar to the setup we used. However,

We also use flutter, and have extensive native code that needs to be compiled for each platform/abi. What you describe is similar to the setup we used. However, more and more developers have opted to get a MacBook in order to avoid the hassle. It might make sense to just have a dedicated mac computer running a gitlab worker that builds the iOS stuff for us.