@pulkomandy
Never really used GNOME Web, but I have used a variety of browsers in Ubuntu for years with dozens of tabs opened, with no trouble at all. Only 8GB of RAM.
Most likely, the cause is a severelly underpowered machine.
Ok, you are right 😅 . I have never gone so far, but had trouble enough compiling NPM dependencies in an old hard disk on Windows. I'm suprised you got to 9.