I heard a lot Manjaro mentioned in the forum. So I believe it should be okay.
I personally prefer Ubuntu, not because it is better but because they have large user base, so it should be easier to find information if I have problem with it. I'm using Ubuntu Mate, it is a lightweight flavor of Ubuntu. Linux Mint, which is a non -official flavor of Ubuntu, is frequently mentioned in the forum. You should consider Linux Mint too.
For your information, some years ago Lazarus had installation issues with Ubuntu, Mate and Mint. But as far as I know recent versions of Lazarus no longer have that problem.
I ever tried Manjaro, Fedora, Ubuntu, Lubuntu, Xubuntu, Ubuntu Mate, Linux Mint, all of them are very easy to instal. Just some clicks, provide some information and wait.