After some search for programming languages which promise to reduce the number of bugs, I decided to give Ada (2012) a try.

I like it better than C and C++ and the compiler is included in Debian in a reasonably recent version that it can compile the code that I need.

Ada is particularly nice for programming RPI 2040 microcontrollers because for my needs I didn't need additional libraries. For both of my RPI 2040 projects (one of which is online here: https://masysma.net/37/dcf77_vfd_raspi_clock.xhtml), my code had fewer bugs than I had anticipated.

For general purpose systems programming the lack of free software libraries is still a concern e.g. while working on a custom backup restore program I had to write my own LZ4 extractor and Blake3 hash function implementation because there wasn't any existing libraries that I could find for the purpose.

In my experience it is trivial to call out to C libraries from Ada. You run a tool to convert the header file to Ada syntax, you link in the C library, and then you call the C code as if it were Ada code.

That's probably why you don't find LZ4 and Blake3 libraries. You forgot to look for the C libraries, which many Ada users would use.