A nano VNA is inexpensive enough that I won't work hard to discourage you from buying one.
Let's just say you can build a good antenna for HF without one. An SWR meter can tell us if our antenna is to long or short. Very little inside a ubitx or bitx can be measured with one.
I work as an EE, been a ham for decades. Yes I will get one eventually. But most hams do well without one. But if you are curious and want to learn, sure, get one.
73 curt wb8yyy