I use an old 2008 iMac running Linux frequently and it runs remarkably well. Firefox and MS Edge are certainly the apps that bring it down from a memory perspective ( it only has 6 Gigs ). Electron apps like MS Teams are right up there though and make it chug even more than the browsers do.
To be fair, I have dozens of tabs open including beasts like GMail but I certainly have to restart the browsers from time to time.
Compiling huge C++ code bases is a memory nightmare as well.