You could download stressapptest and run that memory benchmark in the normal system.
I’m not sure how well the current version of Memtest does, but when I was overclocking I was told not to use it as it couldn’t reliably get memory to crash. (Funny problem to have). The two recommended tools are Windows only, so I found stressapptest as the best alternative.
If you only need file syncing, there are better options than Nextcloud. But Nextcloud is the only real option if you want to create a full suite of replacements for office365 or google thanks to the large plugin ecosystem.