postgres restore configuration?
Have you tried parallel pg_restore, i.e. the -j flag?

fsync=off can be better than just synchronous_commit=off.  In fact, the latter might not do much at all because most of the loading should be done in large COPY commands which wouldn't be committing until the end anyway.

You can also try increasing max_wal_size.

Finally, use tools like top, vmstat, sar, perf, or strace to figure out what the bottleneck is, IO, CPU, or perhaps network or something else.