The generally-agreed rationale of UBI is that growing use of automation might eventually make it hard for people who lack relevant skills to support themselves even by working

That's an often-quoted reason, but it's far from "generally-agreed". For one thing, there is the obvious retort to it: we'll consider UBI when the robots actually make people unable to "support themselves even by working" and not before that.

A lot of people (e.g. Charles Murray) support UBI as a less-painful alternative to the metastasizing bureaucracy of welfare, etc., and with less mis- and disincentives, too. It is basically seen as a welfare equivalent to the "taxes on a postcard" (or maybe flat tax) movement.

The generally-agreed rationale of UBI is that growing use of automation might eventually make it hard for people without skills to support themselves even by working, at least for broadly reasonable working hours and conditions.

Various people support UBI for different reasons. It's not true that nobody in Germany calls for UBI. You might personal oppose UBI in a country like Germany but that doesn't mean that other don't want it.

Milton Friedman also wasn't concered about growing use of automation when he proposed UBI as negative taxation.