Now that we are all going to have to dive into our router configurations, wouldn't it be a good time to make some changes that are long overdue?
Like getting rid of the IPIP mesh and replace it with something more modern and supported by off-the-shelf routers, works behind NAT, etc? I would say setup some routers with VPN of different types around the world, have everyone connect to there using a suitable VPN protocol, run BGP on it to announce the gateway subnets.
A $50 MikroTik can do those jobs, for those that still want to run a JNOS system on MS-DOS they can put one in front of their box and still use it. People are already using it for IPIP mesh, a change in topology would be only a config change for them. And other routers mentioned here can do it too, without having to get external programs installed on them.
Those that want direct connection without a centralized system in the path can simply setup a VPN connection between them and configure the BGP peers, it will automatically work. There is no need to use only a single protocol in such a network, only the peers have to agree, so you can select from anything like L2TP/IPsec, OpenVPN, Wireguard, just plain GRE or even IPIP, etc etc. Just at this time I am trying to move my colocated machine that runs as an IPIP mesh member and I face that stupid "protocol 4 is not passed by the firewall" problem again. Arghh!!
Also we could get that IPv6 idea going. Remember it has been discussed many times and the only things we still need is some agreement on how to register and distribute the "list of AMPRnet prefixes in IPv6 space". Again that could be done using BGP, no need to setup yet another registration portal with downloadable files.
Note that Daniel EA4GPZ put some ideas around IPv6 on his site: https://destevez.net/ipv6-for-amateur-radio/
Rob