nasm or yasm will work. I only have experience building it with nasm.

But yes that is indeed a dependency. Personally I do not see the problem with adding nasm as a build dependency, as it opens up possibilities for even more performance optimizations in python by moving parts of the code to Assembly. But I can imagine that there might be complications with updating the build system.

Libdeflate does not have this problem as it entirely in C. So it could be interesting to use that. I think the unfortunate use of memory is due to the libdeflate-gzip coding, and not necessarily because of the library. Samtools is a tool that uses libdeflate library to great effect and its memory usage is fine.

> No, the bug tracker seems fine for this.

Well one thing is that libdeflate and isa-l use different compression ratio's for the levels. isa-l does not support anything above 3. libdeflate supports 1-12. So it is not a one-to-one mapping.