They do hash MAC addresses, but they upload your entire Dmesg log, list of network interfaces (including virtual; VPN, bridge, Docker, etc), list of kernel modules with their configuration, list of partitions with their filesystem and size, list of all systemd units (services, sockets, and timers), list of all packages installed (from APT, I use Ubuntu).

Maybe run this from a Live CD rather than your system.

Also note that hashing MAC addresses prevents someone from getting your MAC address by looking at your report, but does not prevent anyone from finding your report if they know your MAC addresses.