I have an older set of Samsung Washer & Dryers, but they should still connect to the 2.4GHz network. They are in the same room as the Google Nest Wifi Pro (they don't allow you to turn off 5GHz, unfortunately, it's always 2.5, 5 & 6.)
But I had an old Wifi extender, and I put that in 2.4GH only mode with a different name than my network but connected it to the Google Nest Wifi Pro to make sure I had internet access, which I did.
I did the same process to set them up. I don't have a SmartThings QR code on them so had to add them manually, by pressing the Smart Control button until AP appears. My phone does find the washer and dryer but quits at connecting to the Wifi repeater, which is plugged in directly behind them. I recall in the past when I tried this that you could find the model number but maybe that's changed with the new app.
Also, I have a brand new Samsung Dishwasher that connected flawlessly to SmartThings before I tried this setup. So it's definitely something with the Washer/Dryer. All my other Samsung equipment is connected to the network fine.
