Linux on a Skylake-era i7-6820HK (quad core, ~3.2ghz) runs modern GNOME or KDE just fine. I had 64gb of ram and had cleaned the guts and installed a slightly bigger/faster NVMe to use in the last year. It runs LibreOffice or GoogleDocs just fine. It's slow to finish big compiles owing to 4 slow cores, but it's responsive even when bazel is doing its best.

The biggest issues I have with my system is that even with a brand new battery, battery life on 45W Skylake portables isn't ideal (this system is nearly 10 years old now), yielding about 2.5 hours with light browsing or terminal work. The 4k IPS screen is also dim-ish, but I remember it being pretty nice for the era in late 2015/2016. Compared to an M3 macbook pro is like the moon compared to the sun. This isn't inherently an issue with the CPU though.

If you leave the laptop plugged in, it's fine compared to a modern machine. Connected to an external display to avoid the dim screen and I'm able to do my programming/administration work just fine. I don't need a ton of cores to run GNOME powering Chrome and Kitty + tmux + ssh.

My portable machine is a Motile M141 with a Ryzen 3 3200U. That's a 2-core 4-thread CPU from 2019. It's pretty smooth for older/less graphically intensive videogames, cloud game streaming, light Python software development in even heavy IDEs like PyCharm, playing around with SDRs in the field, having a few dozen tabs on Firefox, etc. It plays back HD and 4K videos just fine. When the battery was fresh I was getting close to 7.5-8 hours of battery life; after five years of lots of portable use it is more like 5ish hours of battery life.

The only real upgrades I did was bump it to a 16GB stick of RAM and add bump the WiFi to an Intel 6E 210. I'm contemplating getting a new or secondary NVMe for it. The only real complaint I have is it doesn't charge by USB-C.