You can download STMViewer from here.
Here are the installation instruction.
I believe it needs at least version 13.2 of GDB (issue).
I am compiling with platformio using -g -ggdb build flags, this ensures proper information are available in the .elf file.
I made a short video showing basic usage of the tool.
If you change your program, the memory addresses might change, so you need use the Update variable addresses button.
This should support different model of stlinks and should work on STM32 only.
But it works for me with a Chinese STlink V2.1 clone and GD32F103/GD32F130 chips also.