Using FreeBSD 12.1-RELEASE-p1, I was getting linker errors with DEFAULT_VERSIONS+=ssl=libressl set when trying to build either irc/eggdrop or irc/eggdrop-devel. I noticed in the config summary it detected OpenSSL and not LibreSSL:

"SSL/TLS Support: yes (OpenSSL 1.1.1d-freebsd  10 Sep 2019)"

Here is the specific log: 

    ---------- Yeah! That's the compiling, now the linking! ----------

    Linking eggdrop (standard build).

    cc -O2 -pipe  -fstack-protector-strong -fno-strict-aliasing  -pipe -Wall -I.. -I.. -I/usr/local/include/openssl -DHAVE_CONFIG_H  -o ../eggdrop bg.o botcmd.o botmsg.o botnet.o chanprog.o cmds.o dcc.o  dccutil.o dns.o flags.o language.o match.o main.o mem.o misc.o misc_file.o  modules.o net.o rfc1459.o tcl.o tcldcc.o tclhash.o tclmisc.o tcluser.o  tls.o userent.o userrec.o users.o  -L/usr/local/lib -L/usr/local/lib -ltcl86 -lm -lpthread -lz -lssl -lcrypto md5/md5c.o compat/*.o `cat mod/mod.xlibs`
    ld: error: undefined symbol: SSL_is_init_finished
    >>> referenced by net.c
    >>>               net.o:(sockread)

    ld: error: undefined symbol: SSL_is_init_finished
    >>> referenced by net.c
    >>>               net.o:(sockread)

    ld: error: undefined symbol: OPENSSL_hexstr2buf
    >>> referenced by tls.c
    >>>               tls.o:(ssl_fpconv)

    ld: error: undefined symbol: OPENSSL_buf2hexstr
    >>> referenced by tls.c
    >>>               tls.o:(ssl_fpconv)

    ld: error: undefined symbol: OPENSSL_buf2hexstr
    >>> referenced by tls.c
    >>>               tls.o:(ssl_getfp)

    ld: error: undefined symbol: OPENSSL_sk_pop
    >>> referenced by tls.c
    >>>               tls.o:(ssl_verify)

    ld: error: undefined symbol: OPENSSL_sk_free
    >>> referenced by tls.c
    >>>               tls.o:(ssl_verify)

    ld: error: undefined symbol: OPENSSL_buf2hexstr
    >>> referenced by tls.c
    >>>               tls.o:(ssl_info)

    ld: error: undefined symbol: OPENSSL_buf2hexstr
    >>> referenced by tls.c
    >>>               tls.o:(ssl_info)
    cc: error: linker command failed with exit code 1 (use -v to see invocation)
    *** Error code 1

    Stop.
    make[3]: stopped in /wrkdirs/usr/ports/irc/eggdrop/work/eggdrop-1.8.4/src
    *** Error code 1

    Stop.
    make[2]: stopped in /wrkdirs/usr/ports/irc/eggdrop/work/eggdrop-1.8.4/src
    *** Error code 1

    Stop.
    make[1]: stopped in /wrkdirs/usr/ports/irc/eggdrop/work/eggdrop-1.8.4
    *** Error code 1

    Stop.
    make: stopped in /usr/ports/irc/eggdrop

I fixed this with a simple update to the Makefile:

    --- Makefile    2019-12-30 12:29:49.917497000 -0600
    +++ Makefile.new        2019-12-30 12:30:10.378109000 -0600
    @@ -19,7 +19,9 @@
    
     GNU_CONFIGURE= yes
     CONFIGURE_ARGS+=--with-tcllib=${LOCALBASE}/lib/libtcl${TCL_SHLIB_VER}.so \
    -               --with-tclinc=${LOCALBASE}/include/tcl${TCL_VER}/tcl.h
    +               --with-tclinc=${LOCALBASE}/include/tcl${TCL_VER}/tcl.h \
    +               --with-sslinc=${OPENSSLINC} \
    +               --with-ssllib=${OPENSSLLIB}
    
     MAKE_JOBS_UNSAFE=      yes
     LLD_UNSAFE=    yes