First smartphone: 1992
The EO 440, which, I admit, was more a phablet (a la el reg), had a cellular capability; sure you could do voice. but the system was set up to also allow interactions over the cellular network via it's decimal communication system (aka you pressed numbers on the telephone, but it did it for you).
Remember: this is BEFORE the WWW.
So Nokia liked this, even though AT&T had big money in EO. (Technically, Nokia was investing in GO, a doomed Bay Area Company, while AT&T was investing in EO, a similarly doomed AT&T wipe-out; EO swallowed GO because AT&T said it was good to eat and then chocked to death because EO's executive in AT&T had failed to meet his targets.)
So EO had phablets, but it also had, in development, a smartphone; the EO220, aka "Loki", (the 440 was nicknamed "Thor" and the 880, which was a big <senseid>, was nockgnomed "Odin". The 220 was pretty much everything a smartphone would be.)
Of course Nokia got clockwise-#8'ed (though they did Sue, though the wrong people.) The Engineering Misdirector #8'ed off while accusing people of being "rats leaving the sinking ship" and became something associated with Marketing and the Newton (more his capabilities I think.)
The intelligent people got new jobs with old companies; perhaps the most intelligent went to work with Sun, on Java. This was 1993; you have to think very carefully about where Java was then.
And there were no more smartphones until Nokia recovered, late, from being #8'ed by AT&T, and developed the best smartphone operating system in the world, which then died. So now we are left with Dinosaurs, and this was all before the big sweaty black turtleneck presented his Product.
That is my opinion.