You should be able to migrate most or all of your existing Hyper-V VMs to Proxmox, which would be relatively straight forward. My recommendation would be backing up everything to your TrueNAS (that has the dedicated HBA) then you can wipe your Windows boot drive and install Proxmox. Then you could start by migrating your TrueNAS VM over and passing it's HBA back to it.
Yeah I thought about this being the easiest way to do it. I just wasn't sure if TrueNAS would come back up and just recognize the disks and start working. I have backups of everything and I've tested restoral. I would prefer to not have to go the backup restoral route as it's more a scorched earth option. My other VMs I'm not really concerned about, it was mainly the NAS.
I don't really have any experience with PVE, but I want to learn. I've been learning about docker containers more recently, I like learning new tech so I'm all for it. My main PC has been running Linux for about 6 months now and I'm just trying to get away from Microsoft in general. Thanks for the info.

Why don't people like the audiobookshelf app?