1. Standard host on Proxmox, BIOS=SeaBIOS. SATA0 reserved for loader img. add additional data storage HDD on SATA1. setup boot media from SATA0. add serial port for you troubleshooting.
**Pay attention on network, use Intel E1000 instead of VirtIO ** - VirtIO cannot get IP address on network (My experience)
2. copy synoboot.img to /var/lib/vz/image, convert img to qcow2 by qemu-img convert, my qm host ID is 100, please modify to yours.
** example: qemu-img convert -f raw -O qcow2 /var/lib/vz/images/100/synoboot.img /var/lib/vz/images/100/vm-100-disk-1.qcow2
3. import disk by qm inportdisk
** example: qm importdisk 100 /var/lib/vz/images/100/vm-100-disk1.qcow2 <your-qve-disk>
4. back to Proxmox devices setting, attach disk as SATA0.
5. qm start 100 and monitor on serial port.
6. find.synology,com or find IP from your router, using 3617xs 6.2-23729.pat, after launch system, update to 23739 update2.