Buundo
Pick a name. Your address is yours until you release it, and it stays the same on any network.
A token connects one laptop to Buundo. Create one per device; revoke it if the device is lost.
New token: copy it now, it is not shown again.
This makes your local server public. Only share what you mean to share.
Install the app, or the buundo command, and sign in with your email. It creates its own laptop token; you don't need to copy one.
curl -fsSL https:///install.sh | sh buundo login buundo http 8000 --name myapp --host-header myapp.local
Save as frpc.toml, put a laptop token in it and run frpc -c frpc.toml.
They sign in with an email code and choose their own username.