Hey Adam, welcome!!
I tried to ride Saleve once, but took a wrong route and ended up carrying the bike more than riding it

Am sure there must be some routes off there, but like most places around here, it often isn't well marked (or marked at all) so can be hard to find.
There is some good XC in Metabief, just over the border in France, also around the Lac de Joux...but not sure easy they are for you to get to.
I would imagine there must be some riding off St Cergue, but I've not been up there. I'd be interesting in joining a group trying it out though for sure.
Can't wait to get the bike out again and hit the trails.