Issue resolved after updating to the recent 2.2.1 release of LibreSSL.
$ ldd /usr/local/bin/tor | grep -E 'lib(ssl|crypto)'
000002abd12ad000 000002abd170c000 rlib 0 1 0
/usr/local/lib/libssl.so.33.0
000002abee2d2000 000002abee8a0000 rlib 0 2 0
/usr/local/lib/libcrypto.so.34.0