It is not a future-oriented solution to require an old version.
Apart from that, the bug has already been closed in https://github.com/vyos/vyos-documentation/pull/1562 - unfortunately I forgot to close the issue here as well.

The server code is (unfortunately) proprietary, but the client is open source (and even in F-Droid).
With my FR I meant the client and not the server part, so VyOS can be part of a tailnet.