My opinion is that you should verify the hardware first, before worrying about a RAM upgrade.
Only you can decide whether particular hardware that doesn’t work is important e.g. if web cam doesn’t work then that might be unimportant to your particular situation or it might be important.
Edit: PS You may be able to trick the installer if you install on an external drive using a computer that does have 4GB RAM and then move the external drive to the computer that only has 2GB RAM.
And in this case, what might be the result? Will the computer just slow down?
Sometimes it is better just to do it and find out !
It is possible that it will fail to boot, due to an explicit check during boot. It is possible that it will fail to boot, because it runs out of memory during boot.
It is possible that it runs out of memory subsequently once you start running applications e.g. a web browser.
It is possible that it starts to run slowly due to swapping, if you create and enable a swap file.
@irvinewade, I confirm that after the complete installation to a flash drive on a computer with 16GB of RAM, this new bootable system won’t boot or start on the old laptop that warned me about the RAM requirements of 4GB and not 2GB. If there is another reason for this I am unsure. So this is a confirmation of what has been said, Live USB worked but not the installed PureOS on the same laptop.
That’s too bad. In that case I would revert to
otherwise pick a Linux distro that is more lightweight and which supports a computer with only 2GB RAM.