Subject says it all. I've been trying to figure out which computer programs play 9x9 with trained network and so far I've only found KataGo. Converted weight files are available for LeelaZero, but no independently trained network weights, AFAIK. I haven't found any info on PhoenixGo, though

PhoenixGo cannot directly play 9x9 networks. You need to modify the source code to customize the input feature layer according to your needs. So the conclusion is not feasible.