Is there any way to install FreeBSD using OVH panel? When I try to use panel to reinstall VPS there's no option to choose FreeBSD as OS.
OVH recently removed the FreeBSD installation images, I think because FreeBSD 13 was released and they have not had the time (or motivation) to see the trouble of creating an installation image for it. I actually just wrote the support and asked if they have plans to make FreeBSD images available again.
Meanwhile, there is a way to install FreeBSD (or any other OS) from custom ISO. It's a bit tricky since you have to run qemu from the VPS rescue mode console, and then attach to the qemu session using the Spice remote viewer. It's not too hard though, and if you have any experience of tinkering with stuff like this then it should not be a show stopper.
Note that you should use the FreeBSD "bootonly" (net install) ISO file when performing the procedure described below.
Instructions on the custom ISO installation can be found here:
https://community.ovhcloud.com/t/35253