You as maintainer can consider this serious enough for keeping the
package out of trixie, but in general this is not a release critical
bug since no old binaries exist on these architectures.
The normal and easiest solution would be to use
Architecture: any
which would automatically build on all architectures where luajit is or
becomes available.
If the package always FTBFS on mips64el, riscv64 and s390x that's a bug
you can try to fix or ignore - the build failure itself is not a problem.
cu
Adrian