Does Vyos support Hashing of flows when using OSPF ECMP? Or is it locked to per-packet round robin?
You have options for choosing hash policy.
FRR ECMP documents: Zebra — FRR latest documentation
Linux Kernel information: https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt
And vyos command:
set system sysctl parameter net.ipv4.fib_multipath_hash_policy value