Running from a terminal window reveals why:
"[16268:0203/212859.867721:FATAL:setuid_sandbox_host.cc(157)] The SUID sandbox helper binary was found, but is not configured correctly. Rather than run without sandboxing I'm aborting now. You need to make sure that /opt/yakyak/chrome-sandbox is owned by root and has mode 4755."

-rwxr-xr-x 1 root root 5581136 Jan 22 15:25 /opt/yakyak/chrome-sandbox

Why do we require a suid-root sandbox to run yakyak 1.5.4 now? What changed here?