wxsqlite3 | Outdated and please refer to author 's repo

1. There never existed a version 3.11.1 of wxSQLite3. However, there was a release of SQLite 3.11.1 in March 2016. Current version of SQLite is version 3.23.1.
2. wxSQLite3 is mainly a thin wrapper for the SQLite library for wxWidgets based applications. Are you developing a wxWidgets application? Or are/were you just using the SQLite library with encryption extension that is included in wxSQLite3?
3. Starting with wxSQLite3 version 3.5.0 the included build system was overhauled, making it easier to build wxSQLite3 under Windows and Linux. Up to version wxSQLite3 3.5.9 pre-generated build files were included for the wxWidgets wrapper library only, but a premake5 script for generating build files was included. Since version wxSQLite3 4.0.0 pre-generated build files are also included for the SQLite library with encryption extension.

So, my advice would be to download a recent version of wxSQLite3 and try the included build files for Linux (and other Linux-like systems).

The C/C++ code seems to be alright. And if the test application could be compiled correctly, obviously a valid link library was used. However, the runtime error message indicates that the correct DLL was not loaded.

This indicates that the pre-compiled SQLite DLL was not copied into the same directory where the executable of the test application resides, or it was not in the search path of the application. However, some SQLite DLL was found in the search path, but most likely an "official" SQLite DLL that does not include the encryption extension.

Make sure that the SQLite DLL that includes the encryption extension is accessible by the test application.

The pre-compiled binaries from the wxSQLite3 releases definitely include the entry points sqlite3_key and sqlite3_rekey.

It's because you have a local uninitialized Grid1 in your function that is hiding the class member that you initialize in your constructor. Get rid of that and use the class member.