Repeating Groups are simply – and only – a way of visualizing the elements in a list. If you create a list of n "HELLO"s, your repeating group will visualize them for you.
A list is a list. (It’s just a one-dimensional array.) Of course, you can’t create a list of n of the same values in vanilla Bubble easily.
But you could create a list of n numbers via any number of means (Toolbox’s List of Numbers element, List Shifter, Floppy’s “Create Numeric List” action, etc.) and then use that list of numbers as the source for your RG and then, in the RG’s cell, just have a text that says “HELLO”. But… WHY? (Don’t tell me the answer because I don’t desire to know. The question is hypothetical.)
Repeating Groups display “Lists”. (And won’t display anything that isn’t a List). The “Data source” for a repeating group must be a List. Otherwise it just won’t work as you have found out.
The word “hello” is not a list. Any single thing is not a List. It’s a single thing. A single image, a single URL - no single thing is a List.
So you need to provide a List as the Datasource to a Repeating Group. If you don’t have a datasource as a List - your repeating group has no list to display.
An RG is for holding (and usually displaying) a list of data…
If there’s no data defined in the initial DataSource (or sent to the RG in a display list action) then it won’t display anything, regardless of what you put inside each cell… as each cell refers to one item in the list of data…
If there is no data, then there are no cells, so nothing inside the cells will be displayed…