In this post, you will find a component that you can use to validate screen flow input components that do not support input validation.
There is a standard input component almost for any data type. For instance, text, number, checkbox, date, etc. Although you can configure them to be required fields, there is no way to make the screen components read only.
There are many available standard input components in screen flow. However, in some cases, they may not be enough for your needs. In those cases, you can build or install Lightning components for flow screens.