My dog has started barking at other dogs on walks

i’ve read other posts about similar situations and have found that he’s probably going through a “frustrated greeting”. he is an extremely friendly dog without a bad bone in his body, and loves playing with other dogs. the other posts got a lot of good advice to help curb this behavior, but it all revolved around treats. my dog is not treat driven, he will completely ignore them outside of the house, no matter the flavor. is there anyone out there who has dealt with a frustrated greeter that also doesn’t accept treats? looking for anything here, he is a beagle mix so his barks aren’t barks, they’re bays, and very frustrating to hear at 7 in the morning and make me feel awful for the other person walking their dog who could also have a reactive dog.