Alright, you know what? I'll be switching.

Hello there. I'm a beginner so keep that in mind. I have an old laptop (something like 10 yo). It has an HDD, 4 gigs of DDR3, an i3 4th gen 1.7... #linux

https://kbin.social/m/linux/t/371397

Alright, you know what? I'll be switching. - Linux - kbin.social

Hello there. I'm a beginner so keep that in mind. I have an old laptop (something like 10 yo). It has an HDD, 4 gigs of DDR3, an i3 4th gen 1.7...

I think that EndeavourOS with XFCE would be lightweight enough, but I’m not sure if it’s as reliable as Mint, I have used it for few days only.
KDE in 8GB RAM won’t leave you much room for applications. If you can’t get more memory, I suggest trying a lighter desktop environment, or maybe using ZRAM or ZSWAP.
8GB of RAM for KDE Plasma should be more than enough. I'd say starting at 4GB and below that you'd run into problems. I'm saying this as somebody that has Firefox with several tabs, Libreoffice, two heavy electron apps, an email client and other miscellaneous bits and bobs open while only using just under 6GB of RAM.