Is it safe to share mobile internet via a hotspot from a phone with an active VPN to a laptop?

IT IS SAFE, BUT TRAFFIC FROM THE TETHERED DEVICES GOES DIRECT AND UNENCRYPTED BY DEFAULT.

A smartphone's built-in hotspot broadcasts regular cellular internet, bypassing the phone's active tunnel. Connected laptops access the network in the clear using their standard IP addresses.

Hotspot Gateway Isolation

A smartphone's operating system separates the network stack for incoming tunnels and the built-in Wi-Fi router interface. Without specialized root utilities or third-party redirection software, mobile devices route third-party gadget traffic through the cellular carrier's direct gateway, completely ignoring the active encryption client.

Install and run an independent security client directly on the receiving laptop.
Use specialized tunnel relay apps (VPN Hotspot) if you have superuser (root) privileges.
Set up a proxy server inside your mobile client and configure its local IP in the laptop's network settings.
Run a mobile tunnel on a portable 4G router that supports built-in configurations.