Do you want to upload more than one file at a time to Flow?

If so,I've made a demo(Upload multiple files at once and save them into the SP library) for your reference:

1\Add a Attachment control(AttachmentControl)
2\Add Timer control(Timer2)

Duration

3000 /*loop in 3s*/

OnSelect

Clear(TheFiles);Set(TheCount,1)

OnTimerEnd

Set(TheRecord,Last(FirstN(AttachmentControl.Attachments,TheCount)));Set(TheURL,TheRecord.Value);Collect(TheFiles,{FileName:TheRecord.Name,FileContent:Substitute(JSON(Image1.Image,JSONFormat.IncludeBinaryData),"""","")});Set(TheCount,TheCount+1);Set(TheFilesJson,JSON(TheFiles,JSONFormat.IncludeBinaryData))

Repeat

TheCount<CountRows(AttachmentControl.Attachments)

3\Add an image control(Image1)

Image

TheURL

4\Create a flow(PowerAppV2 -> Compose)

The Schema

{
 "type": "array",
 "items": {
 "type": "object",
 "properties": {
 "FileContent": {
 "type": "string"
 },
 "FileName": {
 "type": "string"
 }
 },
 "required": [
 "FileContent",
 "FileName"
 ]
 }
}

5\Go back to the app and add the flow into the app

6\Add a button(Button5) and set it's Onselect property: