The premise I responded to was that UBI was the only way to free up OSS maintainers, and that they wouldn't care about the lost hundreds of thousands of income if their basic needs were met. My point was that if this was the case, you would already see the low-hours-per-week strategy in place as a non-trivial factor in OSS funding. And yet you don't, because the foundational assumption is incorrect.
Also note that 10 hours a week is hyper-conservative. The population of people maintaining OSS projects are more than capable of pulling eg $70/hr for contracts[1], especially at the low volumes we're talking about. To reach UBI levels of income at this rate would require _1.5 hrs/wk_ of work, or 6 hrs per MONTH. This allows you to drop the required talent level pretty low, despite already pulling from a population that's selected for "ability to maintain a useful OSS project".
[1] also very conservative: I wouldn't be surprised if a median estimate came closer to $150/hr for your average OSS maintainer
