I don't have a program that uses it, so it's not my place to watch mailing lists for it getting deprecated. Basic searching of Github however (what I'd have expected them to do before removing it) reveals 20k files that contain IPPROTO_UDPLITE, and many projects that use it directly. Probably the most renowned is FFmpeg (!!!).
It is not breaking userspace if there are no programs in userspace that care.
If you have a program that cares please report it.
The evidence is that no one has had a program that cares since 2016. A decade of holding on to dead code seems enough.
I don't have a program that uses it, so it's not my place to watch mailing lists for it getting deprecated. Basic searching of Github however (what I'd have expected them to do before removing it) reveals 20k files that contain IPPROTO_UDPLITE, and many projects that use it directly. Probably the most renowned is FFmpeg (!!!).
https://github.com/FFmpeg/FFmpeg/blob/master/libavformat/udp...
https://github.com/search?q=IPPROTO_UDPLITE&type=code
https://github.com/tormol/udplite
https://github.com/nplab/packetdrill
https://github.com/python/cpython/blob/4e96282ee42ab51cf325b...
https://github.com/search?q=repo%3Aviveris%2Frohc%20udplite&...