It is a Chinese MIPS-based Arch

It is a Chinese MIPS-based Arch

Originally Loongson started with MIPS, but Loongarch is a different, although similar instruction set (just as Alpha and RISC-V also have similarities with MIPS). Not just the mnemonics are different, but also the encodings (otherwise one could just reactivate the Debian MIPS port for Loongarch. E.g., Loongarch "add.d r1, r1, r1" encodes to 0x108421, while MIPS "daddu r1, r1, r1" encodes to 0x21082D.

One interesting aspect is that many instruction sets with 32-bit and 64-bit variants define the regular add from the 32-bit architecture to work on 64-bit values in the 64-bit variant (e.g., SPARC, Power, RISC-V). Some (RISC-V) define a 32-bit variant that sign- or zero-extends the low 32 bits of the result. MIPS instead defines the regular addu from MIPS-I (32-bit) as the sign-extending variant and defines a 64-bit daddu in MIPS64; Loongarch apparently follows MIPS in that decision.

Concerning "Chinese architectures", as another poster wrote, there is quite a bit of diversity in the architectures used by Chinese companies, including those that are considered to be close to the government by the USA.