This error is caused by sysgensockgui failing to load. The non-loading is likely caused by missing dependencies. One these are resolved, sysgensockgui should operate as intended. Missing dependencies can be checked the following way,
root@r*****a:/tools/Xilinx/Vivado/2021.1/bin# ldd unwrapped/lnx64.o/sysgensockgui
linux-vdso.so.1 (0x00007ffedf51e000)
libQtCore.so.4 => not found
libQtGui.so.4 => not found
libQtNetwork.so.4 => not found
libQtXml.so.4 => not found
librdi_itlib.so => not found
libstdc++.so.6 => /lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007fddc2160000)
libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fddc200f000)
libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007fddc1ff4000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fddc1e02000)
/lib64/ld-linux-x86-64.so.2 (0x00007fddc2367000)