I'm going to be completely honest with you, I really think you need to consider other reasons why people might be depressed in the situation that occurred during the pandemic. I don't know anyone who was doing particularly well, including those working (heck, people at my job at the time were struggling pretty badly with mental health to the point where they started reaching out to us.)
I'm not even saying this as a person that has a strong opinion on UBI, and I am sure some people sincerely believe not having a job was a major detriment for them. I absolutely think it did help me, but the way I see it, it helped because it was something to cling onto for a bit of normalcy, and of course, a bit of social interaction. Outside of the pandemic, a job is not nearly as critical for those two things.
I also do personally think that I still broadly like having a job, and I have had almost no gaps in employment since I started working professionally. That said, if money were no object, I would absolutely take breaks off of professional work for months at a time. For me, I find both professional work and hobby work important in very different ways, and wish I had dedicated time for both. Anecdotally I've definitely known engineers who periodically take months or even a year off of work when they get the opportunity and it seems to be a very healthy thing for them.
The existence of UBI would maybe tempt people to rely on it even if it is detrimental to their lives, but I think it's wrong to draw the conclusion that it's bad because jobs can be a source of fulfillment for many. In the future it's very possible we're going to need to approach the problem from another angle anyways, since there's simply no guarantee there will be meaningful work for us all in the future. (I'm not really convinced there won't be, but it feels unreasonable to consider it outside the realm of reasonable possibility.)