H.264 encodings are using "High 4:4:4 Predictive Profile"
All of the H.264 encodings are using "High 4:4:4 Predictive Profile" by default, which is hardly supported by hardware decoders. That means real compatibility problems with smartphones and (at least most) Intel hardware decoders. Also many propriatery software usually don't even bother supporting this profile.
That happen when feeding RGB buffers to x264, where the default behaviour seems to be to avoid a subsampling and so using a 4:4:4 profile. That can easily be solved by feeding I420 buffers to x264, by applying a caps filter to input datas like this one "video/x-raw, format=(string)I420, colorimetry=(string)bt709". (It may also be solved by specifying an H.264 profile to x264 manually, CF #2012 (closed), but I never tried this solution).