How to connect via ssh to ubuntu regardless of network/NAT and ip?

Question

ubuntu

there is a laptop that travels between offices, you need to connect to it via ssh and upload files there periodically
, how to implement this? Just an external ip and forward nerial ports for the router, there are a lot of offices, routers, too,

how to be? anydesk and similar is not an option, you need ssh

Answer 1

VPN client on a laptop with autostart, I advise ovpn, so that it crawls everywhere
Well, connect already inside VPN

Answer 2

if only for file sharing, then install the syncthing daemon (opensource) or resilio sync (commercial).
p2p sharing the contents of a directory - file exchange directly without servers. channel encryption is no worse than in ssh.
speed at 2.2 GHz wifi + 100mbs LAN is about 6mb / s.