Did you do exactly what the post tells you to do? Did you run:
sudo pacman -Syu blas-openblas
paru is just a wrapper for pacman that includes AUR helper functionality, it doesn’t have any magical properties. You would ahve the same problem using paru.
[sudo] password for emmy:
:: Synchronizing package databases…
endeavouros is up to date
core is up to date
extra is up to date
community is up to date
multilib is up to date
warning: blas-openblas-0.3.23-3 is up to date – reinstalling
:: Starting full system upgrade…
resolving dependencies…
looking for conflicting packages…
error: failed to prepare transaction (could not satisfy dependencies)
:: installing openblas64 (0.3.23-3) breaks dependency ‘blas64’ required by lapack64