Project developers illumos , continuing the development of kernel, network stack, file systems, drivers, libraries and basic set of system utilities OpenSolaris, Then the decision stop supporting the 64-bit SPARC architecture. From the architects available for Illumos, only x86_64 remains (support for 32-bit X86 systems was discontinued in 2018). Termination of support for outdated SPARC systems will allow you to clean the code base and get rid of SPARC-specific restrictions. If there is enthusias, it will be possible to start implementing more relevant modern Arm and Risc-V architectures in Illumos.
Among reasons Favoring SPARC Support Notes Lack of equipment for assembly and testing, if it is impossible to provide high-quality assembly support with the use of cross compilation or emulators. The desire to use modern technologies to use modern technologies such as JIT and the development of components on the RUST ZZK, the promotion of which binding to the SPARC architecture is prevented. SPARC support will also give the opportunity to update the GCC compiler (now used GCC 4.4.4) and proceed to use a newer standard for the SI language.