DNSCrypt fails to start (problem with libsodium)
I managed to refresh dnscrypt-proxy so that it uses libsodium.18.dylib and does not throw the error anymore with the following procedure *:

brew update
brew prune
brew cleanup
rm -fr /Library/Caches/Homebrew/*
brew uninstall dnscrypt-proxy
brew uninstall minisign
brew uninstall libsodium
brew install libsodium
brew link --overwrite libsodium
brew install minisign
brew link --overwrite minisign
brew install dnscrypt-proxy
brew link --overwrite dnscrypt-proxy


* credits to Frank Denis the creator of DNSCrypt.