I had an Aspire One D270 laptop with a 32-bit Intel Atom CPU and 1 gigabyte of RAM, so I installed Debian with Xfce on it, but even then it's running way too slow.
Is there anything I can do to make the laptop faster and more responsive given its limited memory?
You can buy IDE m.2 converter. There are usb to floppy converters, usb drive shows up as floppy drive. You can attach modern peripherals to old computers, this kind of retro world with modern and old parts mixed is funny.
Would it worth, though? I mean, is there a significant difference on IDE between HDD or SSD? With an adapter, SATA speeds on the long run would be bottlenecked by IDE if I'm correct.
Yeah, it's not quick, there is no noticeable difference in speed. Random read should be much quicker. But you can't really buy ide hdds anymore and they will die sooner or later, and the price of small m.2 sata ssds are falling.
I can speak from experience that it is worth it. It won't be a super speed demon, but it will make it somewhat more usable. I've done so with my Asus Eee PC 901 netbook which has the two PATA SSDs. Those SSDs are SUPER slow compared to the cheapest mSATA SSD you can find with more than double the space, and all you need is a MiniPCI-to-mSATA adapter (the Eee PC 901's drive slots are MiniPCI). I documented all about it here: https://claudiomiranda.wordpress.com/2020/10/04/my-geeeky-experiment-part-3/
I'm running OpenBSD/i386 on mine which isn't as fast as something like Linux, but it definitely felt faster even with OpenBSD after the hardware upgrade. I also increased the RAM to 2 GB which is the maximum amount supported.
I acquired an ewaste laptop with an 8 year old celeron, 4GB of memory and a 500GB HDD. I tossed Linux Mint on there as an experiment to see what would work decently on there. Its not great, but its usable and might become my daughter's first computer. Running firefox its noticably slow but I can crack open Libre Office or ScummVM and other than the initial load time it's pretty snappy. I kinda forgot how hard drives give systems that slow-then-fast feeling...