InnerHTML is one of those things that just about entirely goes against the concept of Angular (and 2+ in particular), and thus is really hard to get to work how people want in Ionic.
What are you trying to accomplish? We may be able to offer an alternative.
As to innerHTML: per definition it only accepts a few html tags and sanitises per default (Angular does not trust any input). Irrespective from the point whether you should or should not use it. https://angular.io/guide/security
BTW, I believe there are ways to dynamically insert angualr/ionic components using dynamiccomponentloader and such, and have the angular engine render it, but that is generally very discouraged and barely has a use case for ionic developers, I would think. I tried it once, and it is horrible!