If I think about living only off UBI, or UBI + a passion project, it assumes all the infrastructure and service businesses are still running to make my life comfortable. Will those things run if the motivation is taken away?
* In the big cities, increased rents will almost immediately eat up the extra income from the UBI, and there won't be any meaningful change in the status quo for anyone who rents — which I imagine includes the majority of the people who do the important but undesirable jobs.
* Anywhere that the people doing these jobs either can afford houses (smaller American towns, e.g.), or where there's enough rental supply that rent won't immediately go up by the same amount as the UBI, will have to start paying people more to do these jobs. As far as I understand it, jobs like trash collection are already relatively well-paid given the training and qualifications required, so they might not even have to pay that much more.
I've often wondered if the solution to the "who will clean the toilets?!" problem is: everyone, but only when it's their month to do so.
A pipe-dream, of course, and likely only doable under a military dictatorship.