The DEC677 seems like very powerful hardware, but it has OPNSense installed on board. Can this box be used to install pfSense?
If it runs OPNSense it should run pfsense.
Why not just buy a Netgate 4200 for the same price or even less, depending on the $/€ exchange rates, which also comes with a free pfSense+ lifetime licence?
you are right, netgate will be better
DEC 677 OPNSense
price: 550 EUR
CPU: AMD G-Series SOC
RAM: 4 GB DDR3
Storage: 32 GB SSD
Ports: 4 x 2.5 Gbps Ethernet
Throughput: 5.000 Mbps
IPSec VPN: 600 Mbps
NetGate 4200 pfSense
price: $550
CPU: Atom C1110 /4-core
RAM: 4 GB DDR5
Storage: 16 GB SSD
Ports: 4 x 2.5 Gbps Ethernet
Throughput router: 9.3 Gbps
Firewall: 8.6 Gbps
IPSec VPN: 3.2 Gbps