SCTP generally works and no special support is needed, as you implied it is just payload to IP packets.
Certainly someone is blocking specific IP protocols (considering how many FW guys think ICMP should be blocked), but that would be exception rather than rule, generally speaking all IP protocols work just fine.
Quick test on nlnog ring with
hping3 -c 1 -n 126.96.36.199 -0 --ipproto 132 from about 210 boxes resulted 59 packets delivered, so only 59/210 worked in real-life test.
I've never heard of actual transit provider filtering IP protocols, so it's the enterprise FW protecting the LAN which usually is the culprit. As long as you control the ends of the Internet connection you should be fine.