This is a guide to run Versions like 1.18, 1.19, 1.19.3 and all the versions that need Java 17.
For this example we will use Spigot 1.19.3
Step 1) Download Spigot 1.19.3 and rename it as "custom-java17.jar"
Step 2) Upload the JAR file for example Spigot 1.19.3 to your server. Don't put it in any folder, just upload it.
Step 3) Go to Multicraft Control Panel and select to run Version named "Custom Jar with Java 17"
Step 4) Start your server and play with version 1.19.3