I just today saw there were firmware updates (June 25, 2021) for my smart plugs and started the process. An opportunity for improvement!
It took a number of iterations to get all the devices updated. Between the KP-115's (individual smartplugs) and the HS-300's (smartstrips) I have 44 'outlets' active; I didn't pay attention early on which devices were NOT getting updated, but later I noticed that it seemed to only update one of the HS-300 outlets at a time. I know this for sure because one of the HS-300's was sort-of off-line (it had an IP address, but was non-responsive on the network, and I had to un-plug it & re-plug it back in to bring it "on-line" ... a rather unusual condition in and of itself; we'll see if the firmware update fixes that issue...). When I started the firmware update on that last HS300, I had to initiate it (from the app) six times to get all 6 outlets updated.
That (updating all the outlets in an HS300 powerstrip) ought to be something which could be done in with one 'initiation' by the user in the app.
I also note the prompt which said that the app should be kept open during that process; I did so ... but it's not apparent to me why that is required. Is it really required? Does the app have to be in the "foreground" all the time or can it be just be left open while attention is shifted to another app? (A little more info from TP-Link would be helpful in that "prompt".)
p.s.: The HS300's do not show up in the drop-down list for valid models in this forum.