This is a strong indicator that your PC crashed because of a hardware problem. Use prime95 with the small settings to test CPU stability (minimum 1h). Use memtest86 (the free version) or prime95 with large/memory settings to test your Ram. It could also be your PSU failing/shutting off or shutoff caused by overheating.

What do the system logs say? “sudo journalctl -b-1” after a reboot and jump to the end.

Best solution is to use docker. One container is gluetun which provides the VPN connection. The other container runs transmission or qbittorrent and its traffic is routed over gluetun.