Maybe you join a club, start a band, discover an aptitude for art, start your own business.. who knows?
The problem is not all "work" is equal. The value of the work you do is how much useful economic productivity you generate - how useful what you produce is to other people. The market modulates this by overvaluing productivity which is in short supply (STEM workers), and devaluing productivity which is oversupplied (musicians, artists). This differential pricing then encourages people to "work" in the more productive jobs like STEM, rather than the less productive but more fun jobs like joining a club, starting a band, discovering an aptitude for art (these things are often so unproductive that people have to pay to be able to do them, rather than be paid).
That's the big problem with a UBI. The market prices labor to encourage people to do jobs that are needed, rather than jobs that are fun. A UBI encourages people to do what they find fun rather than what's needed. At first glance, layering a market economy on top of this seems like it would work (i.e. you can still get paid extra on top of a UBI for doing a STEM job). But if you crunch through the math, the pricing for the STEM job then leads to non-UBI income following a divergent series.
Considering how much of what you call "useful" economic productivity is generated by "fun" jobs like art and music,
What do you mean "much"? Very little anything is generated by the fun jobs when you divide the demand by the supply. The market does not reward anything, it's simply the supply/demand curve that determines the price of something, labour included. Due to the supply of artists being so large compared to the demand for art, artists are priced extremely low, and their products are priced just as low to reflect the demand.
your entire premise feels backwards, especially as it does not consider there is a very real drive to push "useful" economic productivity towards zero cost with ever increasing automation.
A small group of artists at Marvel has become an economic juggernaut as armies of artists and artisans translate the comic page into movies and then toys and other banal products for the, as you call them "useful" economic producers to manufacture.
Outliers do not an argument make. The large majority (9999 out of 10000) of "small group of artists" produce works that are worth almost nothing.
A couple of musicians messing around in a garage share their sound and it catches on with clothes, jewelry, etc. geared to the people who want to be part of that scene. Again, giving the, as you call them "useful" economic producers something to take to market.
Yes, a lot of artists are overlooked and underpaid, but that's attributable more to how they are disadvantaged by people who are inclined towards business rather than their true economic potential.
Their true economic potential is close to zero. The markets accurately reflect this. You want a jingle for a radio ad? Almost the entire population can supply you with one. You want designs for a bridge that won't fall down? Only a fraction of the population can give you one.
It's not hard to then say that one class of producer is worth more than the other class of producer. Even with UBI, if everyone can live without needing a job and the majority go on to produce works of art, their value is still considerably less than the minority who use the UBI benefits to learn bridge-design.
UBI won't make artists more valuable than they are now; on the contrary they'll make artists less valuable as the supply of artists will greatly increase (and the supply of bridge-designers will greatly decrease).