And perhaps not just some, as Russia even accused hundreds of Croats to be heading to Ukraine, to join the hundreds allegedly already there: https://balkaninsight.com/2022/03/04/russia-summons-croatian-attache-over-reports-of-mercenaries-in-ukraine/

(They're not "mercenaries", it's how enemy foreign fighters are always called by Russia.)

Croatia also sends weapons. Maybe even including the old American weapons from the war, but probably not because "We are talking about rifles and machine guns with the calibres requested by the Ukrainian side". Or maybe actually the VHS-2 and such, who knows.