The LoongArch ISA is used on CPUs created by Loongson, who have internally created a loongarch64 port that they have turned into an unofficial Debian port called loong64.
Porterbox
There is currently a porter box shenzhou.debian.net. You can also set up your own loong64 sbuild chroot with LoongArch/sbuildQEMU
References
Status: unofficial loong64 port accepted
Discussions: <c32d3af9f9ebc362431e2f208f75b52ba64779c0.camel@physik.fu-berlin.de> <b5a53692-592c-2e3d-a996-a8d6692f4eb1@loongson.cn> <12133b5.b049.182493b9628.Coremail.sangmeng@loongson.cn> <Y0FqIwOJuBMGGHxZ@thunder.hadrons.org> <OS0P286MB0641F6E5B9C3AE7434E9638ACD369@OS0P286MB0641.JPNP286.PROD.OUTLOOK.COM> <37f3f5f2.5495.18432e942d7.Coremail.sangmeng@loongson.cn><1bcbfd39.6450.1843d9f7e2c.Coremail.zhangdandan@loongson.cn>
Mailing list: debian-loongarch
IRC channels: #debian-loongarch, #debian-bootstrap, #debian-ports on OFTC
Documentation: https://loongson.github.io/LoongArch-Documentation/
Unofficial FAQ: https://blog.xen0n.name/en/posts/tinkering/loongarch-faq/