That's client side. FreeRDP needs H.264 libraries to work with this branch of XRDP. Apparently, Ubuntu and variants do not include this in their FreeRDP builds, good to know it's in Debian though.
(MSTSC.EXE and the official macOS RDP client already have H.264 support built-in)
(MSTSC.EXE and the official macOS RDP client already have H.264 support built-in)