At Sandbox 1 in torrc config we have syscall error: https://trac.torproject.org/projects/tor/ticket/29819 The bug was fixed in https://github.com/seccomp/libseccomp/releases/tag/v2.4.1 The detail description: https://github.com/seccomp/libseccomp/issues/148
All versions of tor in portage tree need >=sys-libs/libseccomp-2.4.1.
This is coming down the pipeline for tor-0.4.1.6 and above.