@emil I installed the Home+ 5 app. When I go through bridges and then display accessories, it works fine with the flic buttons. I think there are some bugs in the iOS 15.3 button/switch portions of the home app.
In the past few weeks HomeKit has been tested by a select group of beta testers. Everything is working great and we submitted the app for public release last week but unfortunately it was rejected due to a technicality.
It came to our attention that the general license agreement had been outdated before the approval process was complete, the license agreement has now been updated and as soon as we receive an approval we will resubmit the app for public release.
In other words the HomeKit release is just around the corner. As soon as this happens we will push automatic firmware updates to your Hub LR’s and all you need to do is download the latest version of the app and you’ll be able to get started! We are however unsure when we can get the new approval, hopefully soon.