Well, pip3 and pipx can't install a different version of weasyprint because "pip is configured with locations that require TLS/SSL, however the ssl module in Python is not available." This is not great. What's the point of having a pip without SSL? And answers on StackExchange make me think that perhaps I have to compile something something bla? Oh no…
Back on track! German hyphenation is a go! And you'll be pleased to note that my test PDF consists of the sentence "Ich bin ein Donaudampfschifffahrtskapitän." Or something like it.