Hey there!
For instance, remember there is no pack that is ready to be used, you have to work on it. If you want a ready pack, you can go l2off (advext64) but you will need to pay $$$$ to get anything, literally.
If you want java, which i always recommend as you can be creative and do anything, with no limits. There are packs that has good features, and some are shared(or leaked):
L2fandc - L2jsunrise - l2scripts
For me, i used l2jsunrise (Gold Version)
It was good with minor problems, but there is a serious problem i faced regarding the geo-engine and players falling underground which caused me to close the server to change the files
Then i changed to l2scripts, costed me +1000$
This is the worst decision i have ever ever ever made
The files may seem stable and playable. However, what you would fix in 5 minutes in l2j, you will fix in 30 minutes in l2s, There source is so messy!
Finally, i believed on l2jserver, but heard about l2jmobius, which is based on l2jserver and aCis, which makes it a promising project, in my opinion.
The source is free and all information can be found in their forums https://l2jmobius.org/
My server is expected to launch very soon and my developer is comfortable with the source. But for sure, there will be problems, as i mentioned above, you will always need to work on your files.