Versilian Studios is to be commended for releasing a CC0 orchestra a few years ago. There are a few gaps to fill from freesound. Ideally there would be a Walter fortepiano and a Klavins style felted una corda, which are currently only available from proprietary vendors, but the essentials are already in place (and some extras). My recommendation: since we're a ways away from UBI, buy one of Versilian's paid products as a donation, then let's get to work using their impressive free instruments!