Best design between 2 DC (Catalyst swithches)

Hello

I have 2 DC connected through an ISP QinQ to a Cat3850-12XS and a Cat9500-16X-A.

Obvisouly i need layer2 continuity between those 2 DCs so i simply tag all my VLAN into the ISP QinQ.

The problem is, i'm connected to the QinQ via 1 10G fiber and there is a backup but that is not connected. In case of failure i have to manually plug it.

So i would to connect both link but obviously if i do that, STP will block one of them.

I'm trying to evolve this design, maybe by using VXLAN or other Overlay technology, but i'm not sure that's possible on Catalyst series.

Can you give me your advice?