We had a C++ framework for the 2 mobile+3 desktop platforms at my previous workplace with about 8 people working on it and on average 1 person per platform for

We had a C++ framework for the 2 mobile+3 desktop platforms at my previous workplace with about 8 people working on it and on average 1 person per platform for the UI. Based on that, I don't think it's a good idea to try to go cross-platform for the business logic if you only have 2 platforms with less than 4 devs each. It's also not a good idea to pay mobile dev salary for mobile dev quality business logic code, C++/Rust/etc. will get you better code per money spent. Not to mention the possible issues that could arise with using niche tooling, like the KMP compiler.