Is there any way to do an SVN checkout to the Gitlab freepascal/lazarus repos ??
SVN checkout from the Gitlab repository? No, but
git clone is super easy.
I see you use Windows. Please install TortoiseGit. It recommends a Git installation URL during the process if you don't have it installed already.
Git installation alone is sufficient, too. It comes with very nice GUI tools "git gui" and gitk.
If you work on FreeBSD, git should work very well. I use it on Linux without any extra GUI tools. "git gui" and gitk are enough for my purposes.