If the server itself is running fine you can delete the folder, but if you’re unsure if it has an effect on your server you can move it to a directory outside of your Nextcloud document root first and delete it once your happy with your server.
The HTTP user is different on the various Linux distributions.
BTW a kind gesture like problem solved (i.e. ) or a little ACK to one or more of my comments (i.e. click on the heart icon ) would show you are satisfied. This could be a kind gesture and would motivate me like authors of other advice to continue in lending a hand freely…
The Debian Administrator’s Handbook - Unfortunately, looks as if stuck with Jessie but may be still a valuable source of advice for any system admin aware of the deviations to a more current stable install or to a different flavour of Linux also.