Yes, the French Chess Organisation in 1924 required participants to be amateurs for their Olympiade-Tournament.
The 54 participants from 18 countries had to show a certificate, signed by their national Chess Union, to confirm their amateur status.
They all accepted players, who won price-money in tournaments, but were not recognised as being professional players.
Prize money versus ... what ?
a salary ?
Who were the professionals and how were they different than the prize winning amateurs?
For that matter, how does anyone make a living at chess? Do the tournament sponsors lure the top players to attend by paying them up front? Is most chess income based on winnings or some sort of sponsoring contract? Is most of the money from ancillary activities like speaking fees and selling swag?
Merli, first : realize you are speaking about circumstances 90 years ago !
My words "They all" mean both the French organisers and the national Chess Unions.
Everybody, amateur and prof, could win price-money in tournaments. "Professional" was an unofficial name for players earning money in coffeehouses and exhibitions, ( Blackburne Shilling Gambit ! ) Forget about a salary, there were (few) sponsors, like Nardus for Janowsky.
This forum is about the IOC status. Let's keep it that way.
You can read other sources about the beginning of professionalism, ( Emanuel Lasker ! ), and your last questions are about todays tournaments and todays activities of chess players, quite another subject.
"For the 1924 Olympics an attempt was made to include chess in the Olympic Games but this failed because of problems with distinguishing between amateur and professional players."
If that's true, does anyone know what distinctions were proposed and just who did they conceive should or should not have appeared at the 1924 Olympics?
The unofficial "Olympiad" they held instead did not seem to have any amateurism requirements.