In the latest EdgeLinux it looks like NGinX is not processing uploads due to file size restrictions when proxying. If you connect directly to Antman on port 3000, you can upload your image/iso as normal.
2020/02/11 22:50:42 [error] 26961#0: *1123 client intended to send too large body: 2000990 bytes, client: 10.30.1.10, server: anteggs.local, request: "POST /uploads HTTP/1.1", host: "anteggs.local", referrer: "http://anteggs.local/"
2020/02/11 22:50:42 [error] 26966#0: *1124 client intended to send too large body: 2001008 bytes, client: 10.30.1.10, server: anteggs.local, request: "POST /uploads HTTP/1.1", host: "anteggs.local", referrer: "http://anteggs.local/"