re Switzerland: their songwriting camp is simple
artists can work with composers/producers from all over the world to come up with possible ESC entries, these get judged by a panel usually consisting out of 10 or 12 international jurors whom after closely listening decide whom represents the Swiss at ESC
Austria does internals yes, but their HoD usually teases through clues which 3 are shortlisted by an expert jury
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Malta's MESC is a huge competition on its own
4 quarter finals, 2 semi finals and a grand final

and in the final they have lots of guest act intervals as well
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San Marino basically anyone can submit songs there from any country worldwide, as long as you have the funds to participate