A possible option could be SSTP, which works over regular TCP connections on port 443. But this is not well supported by the Linux world.
Marius, YO2LOJ
SSTP is a star as well. In the open world there is OpenVPN over TCP port 443 when you want to run a VPN over TCP (I would not want that, but that is another topic).
However what it seems to come down to is that these issues can be solved locally. A local Linux server or (e.g. MikroTik) router can be configured to be part of the IPIP mesh and possibly be BGP routed, and then it can serve as a VPN server for local users using whatever protocol(s) is or are locally preferred due to local situation w.r.t. internet routers and/or filtering.
Rob