Try sudo chmod a+x /usr/share/textsuggest/textsuggest-server.
The install script should've done this automatically, I'll see why it didn't work. Thanks for reporting.
That was not the problem. I added execution rights (chmod +x) to all libraries inside /usr/share/textsuggest/libs/, now the server went further and says:
textsuggest-server: symbol lookup error: /lib/x86_64-linux-gnu/librt.so.1: undefined symbol: __clock_nanosleep, version GLIBC_PRIVATE
I suppose that my version of librt.so isn't appropriate for it.
Please check if this build works. If it does I'll upload to itch.
https://gofile.io/d/e92CA5