Understandable, I forgot that this is built ontop of LINTSTOR and not on DRBD directly.
I belive then this post by LINBIT is more appropiate.

This stack which is outlined seems interesting as it means we could for exampel use ZFS as volume manager and create a mirror-1 zpool for fast access, and raid-z2 or zfs draid for the slow access. Utilizing LINSTOR and DRBD for distributing this across the cluster. And utilizing bcache to unify these two zpools for using the fast/slow tier.

I understand that right now the storage controller api of xcp-ng and xo is not setup to utilize such a setup. but could I potentially setup a ext4 or zfs filesystem ontop of this stack and use the already existing storage controller infrastructure, or would I be losing out on either performance and/or features by doing so.

@hellst0rm I don't see why it wouldn't work as long as everything is set to trust your internal CA root. It's pretty trivial to create a CA. I did it years ago because I can't stand cert errors and as a learning exercise. The only annoying part is it's just one more thing to keep track of and update, but if you're running a homelab it just becomes another part of the exercise.