I just updated composer to 1.8.3 and it seems like the never versions are more pedantic about the names of dependencies. It doesn't like uppercase letters and the current composer.json shows the following warning
Deprecation warning: require.JShrink is invalid, it should have a vendor name, a forward slash, and a package name. The vendor and package name can be words separated by -, . or . The complete name should match "[a-z0-9]([.-]?[a-z0-9]+)/a-z0-9". Make sure you fix this as Composer 2.0 will error.
To fix this I ran
composer remove jshrink
renamed it in the composer.json and ran
composer require matomo-org/jshrink=1.3.1