There should be a way to change the “editable” property of a Text Input component in order to disable entry while still showing the value of the text input’s text.
This is especially useful in a situation where you are checking for invalid entries (e.g. letters in a phone number) and wanting to use a substring to delete unwanted characters from a text input. As it is, displaying an alert does not pause other functions on a screen (aha! another feature request? But first, see this) so you can continue entering text while the alert is displayed because the text input is still editable.
This was initially asked about 5 years ago: TextInput Set Editable and also discussed here: Text Input Enable-Disable and here: How do we enable/disable the editability of a text box from the Blocks tab.