I still have my first guitar that I have now owned for more than 40 years. But for my first uke I went cheap and got one of those Alulu ones from e-Bay. It was junk and not worth keeping around. Lesson learned ... you get what you pay for (and sometimes less).
I have my first: Mainland mahogany satin concert. It happened to be a great fit for me...even after I tried out a lot of other brands, tonewoods, and sizes, I still come back to it regularly as a daily player and travel Uke. I’m a bit sentimental about it too so I don’t think I’ll ever get rid of it.
My first dozen or so guitars have faded into the mists of time. Wish I still owned a couple of them, e.g., 1963 Epiphone Sorrento and 1972 Les Paul Custom. However, I till own and play my first 'ukulele, a Pono MT-E from 6 or 7 years ago. It was rather soft and bright at first and now is full and sweet in tone.
I do not. I have never had an instrument that I attached such sentimental value to that I would never let it go. My first uke was nice though as it was one of the early Flukes. I can't even remember who I sold it to. My first stringed instrument was guitar, so I had already gone through some instruments there before I even touched an ukulele.
Yes, I still have the Fender Nohea tenor that was my first. I bought it on Amazon because I had a couple of gift cards. I had read that Koa was the best wood for ukuleles in some reviews. I thought the Fender headstock looked different and it was made of Koa! Wrong! It's a koa laminate body. I knew nothing about setups. It practically took a pair of Vicegrips to barre the 1st fret. Even after a setup it's still difficult to play and the fret ends are very sharp.
I debate about donating it because it's so difficult to play. It has a definite laminate sound.
I recently re-homed my first ukulele (an early Fluke) to a neighbor friend. It was the only one of my ukes that she felt comfortable playing. I miss it from time to time, but fortunately it's only a couple of houses away from me, and I have visiting rights.