https://docs.kernel.org/networking/sctp.html
PS the kernel work goes back to 2003!
It's an interesting protocol, but these days I think the internet has ossified so far that you're probably better off relying on hacks like QUIC and MPTCP to get the protocol features that SCTP stood to introduce.
Though SCTP did find its place as a layer in WebRTC.
My old company/offices had site internet provided by one of the top 50 UK Managed Service Providers. They swapped out the on-site router not many years ago as the fibre to site was being upgraded from 100mbit to gigabit and so a new Juniper firewall with GBE ports was required.
Turns out the newer, faster, shinier, though albeit lower model numbered'd Juniper SRX fundamentally didn't support passing SCTP data and suddenly we lost access to all our remote stuff that used it. Ended up on a call with the MSPs Head of Networks (who was not a stupid person), but their opening gambit was "Are you sure you mean SCTP? Oh. What is that then?"
There was also numerous weird kernel bugs with implementations on CentOS 5, 6 and 7 which all would manage to get themselves into weird states where only a reboot would clear - not really what you want from a multi-endpoint, 'copes and recovers well from network weirdness' tunnelling protocol.
did you file a customer complaint for the device you bought not supporting basic internet protocols? If I look here it mentions "internet" but not TCP or UDP. I'd argue it's false advertising if it actually only supports a percentage of actual internet traffic.
Juniper themselves stated in the manual that this base model device didn't support SCTP, though on ever other level it was faster, more capable and more featureful than the mid-range but much older device it replaced. The MSP didn't have a clue that we (or anyone else for that matter) used SCTP so missed the single footnote mention that the command to enable SCTP forwarding might not be available on some base-level devices.
In their defence, I'm not sure _I'd_ have thought to check if SCTP was supported and I had it running on my network. It works over the internet, it's basically IP, how could it not be suppo---oh.
TCP as originally specified had fundamental design flaws too, but the TCP of today has significant differences from the 1981 TCP standard (not the first version of TCP, but the first version to see significant production use).
Certainly there are things that could be done to improve the ecosystem - but why bother when you can just use a reliability layer on top of UDP instead? And these days there's a "standard" solution so you don't even need to compare choices or worry about design flaws affecting just your program: just use QUIC, everybody uses it and if something goes wrong the world will scream and the shared library will be upgraded by the distro.