I had the same issue... re-linking/aliasing to the existing libraries (libssl.so.1.1 and libcrypto.so.1.1) fixed the issue. A simple `ls -la` helped me figure out what libraries I had...
root@Tower:~# cd /usr/lib64/
root@Tower:/usr/lib64# ln -s libssl.so.1.1 libssl.so.1
root@Tower:/usr/lib64# ln -s libcrypto.so.1.1 libcrypto.so.1
root@Tower:/usr/lib64# ldd /usr/bin/iperf3
linux-vdso.so.1 (0x00007ffe68998000)
libiperf.so.0 => /usr/lib64/libiperf.so.0 (0x00001474185ba000)
libssl.so.1 => /usr/lib64/libssl.so.1 (0x0000147418525000)
libcrypto.so.1 => /usr/lib64/libcrypto.so.1 (0x000014741824b000)
libm.so.6 => /lib64/libm.so.6 (0x00001474180fe000)
libc.so.6 => /lib64/libc.so.6 (0x0000147417f19000)
libz.so.1 => /lib64/libz.so.1 (0x0000147417d02000)
libdl.so.2 => /lib64/libdl.so.2 (0x0000147417cfb000)
libpthread.so.0 => /lib64/libpthread.so.0 (0x0000147417cd9000)
/lib64/ld-linux-x86-64.so.2 (0x00001474187f2000)
root@Tower:/usr/lib64# iperf3 -s
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Server listening on 5201
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