Short update on those who are interested:
The first step after compiling the model was to export the model as a library
lib.export_library("model.so", cc="/opt/riscv/bin/riscv64-unknown-linux-gnu-g++")
Next step was to set up the runtime environment for riscv. I followed basically this straight forward instruction. After the successful build of the runtime library I wrote a small C++ program that includes the tvm_runtime library and reads the model I’ve created before within python. I used the apps/howto_deploy example as reference. In principle I only had to adapt the makefile to my needs (Adapting the TVM root path, setting the riscv compiler) and compile it.
In the end I uploaded the compiled binary and the tvm_runtime library to my device, added the library to LD_LIBRARY_PATH and then executed the binary.