For Bugsnag it's a "Yes and no" answer. If your KMP is a static framework, then yes, it'll work. If it's dynamic, even if you use the crashkios link plugin, it won't work. Since Xcode 15.3 (as far as I could find) there was a change in how unresolved symbols are tracked by the linker. So while it might seem like everything works, when you go and Archive the iOS app, it strips necessary symbols from the main binary resulting in a startup crash of the iOS app.
Crashlytics has the same problem, but just this week I've replaced all the ObjC calls with dynamic calls which don't require those classes' symbols. I tried doing the same for Bugsnag, but to integrate with Bugsnag CrashKiOS really needs access to those symbols. I'll be exploring one other possible workaround for this soon.