Brooks Forsyth

Id recommend Ionic with whichever frame work you are familiar with. That way you get web, iOS and Android. Ionic with capacitor (not cordova) is plenty fast and you can sprinkle in native code when you need it. Ive used it on several projects. I think flutter is good. Its web implementation is not ready yet.

I think the best idea would be to timebox the upgrade to loopback 4. Try to do it in x amount of time and if you are not close to done jump ship to nestjs.