I've have several document libraries on my SPO site that I use the Document Set content type with to organize the files, instead of folders. When I use the SharePoint app on iOS I'm able to view/navigate through the site and click on the libraries, but the document sets appear empty. All files in the document set are not showing and it only shows the default image for a document set. If I tap on the image it opens a blank page. But, if I upload files to the library and don't put them in a Document Set, they show fine.

When you build a custom SharePoint form with power apps, then you will all the sudden realize that some data is recorded wrong because on mobile devices the default form (that does't do the validation you build) appears. This is a really big issue. The custom forms are completely useless when they are not consistent on all devices and the logic can be bypassed (even without the users intention).

What has this to do with mobile first? Why do you prioritize desktop usage so much? In 2018 or 2019, who even considered putting inconsistently different forms on different devices without telling the user?

After stopping the development of InfoPath, this is another dealbreaker for collecting custom business data in SharePoint.