-
Does your router broadcast a 2.4 and a 5ghz connection and are the slow ones only connecting to 2.4ghz? You might be able to force them onto 5 in the router settings or broadcast the different channels under different names and prefer the faster one, it still seems slow for 2.4 but might explain it a bit, especially if there's a lot of local interference on that channel. There are a few WiFi scanning apps for Android that might let you know which channels are best to choose.
snottyotter-
That's probably it. I thought I'd forced things onto 5G in the router settings already, tbh. But I've had to reset the router a few times, so that will almost certainly have cocked things up.
I also used Ookla Speedtest instead of the default Google Search one and things improved considerably, so it could be that as well.
ketsbaia
Laptop and tablet brand new. Laptop is pretty basic, but the tablet is a Samsung Tab S8, so reasonably powerful.