That depends on who set the server up.
Servers provisioned by Laravel Forge
Yes. Ploi can take over a Forge server as it is: same machine, same IP address, sites stay online. Ploi connects over SSH, scans the server and registers the sites, users, certificates, databases, daemons, cronjobs and firewall rules it finds. You start it from Servers, Create server, Import server. The steps, what changes on the server and what to do about certificates are in How do I migrate from Laravel Forge?.
Servers from ServerPilot or RunCloud
Yes. Both platforms run their own builds of NGINX, Apache and PHP, so the import installs Ploi's stack next to theirs and moves your apps onto it, rather than only registering them. Your apps go offline only for the short moment Ploi switches serving over to its own NGINX, about a minute. You start it the same way, from Servers, Create server, Import server. See How do I migrate from ServerPilot? and How do I migrate from RunCloud? for the steps and details. RunCloud servers on the NGINX or NGINX + Apache stack are supported; OpenLiteSpeed is not.
Servers you set up yourself or with another panel
No. Ploi does not know what is installed, how it is configured or which directory layout is used, and guessing wrong would break your sites. Create a fresh server in Ploi instead, add the sites there and move the files over with git, SFTP or rsync. Databases move with a dump and import.
