SQL Server 2019 - Alwayson AutoSeed Sync very Slow for 30 TB database

Question

Dear Experts,

We are using SQL Server 2019 Alwayson AAG with Per DTC check enabled with Auto Seed Option. We are experiencing the Slowness in the AAG Auto-seeding to the Secondary and DR replica.
Here is the Structure followed,

• We have dedicated HeartBeat Network IP's to each Replica inside the cluster which we used during the AG setup.
• Per DTC is checked
• Cluster has a Local instance on each node of the cluster joining the AAG
• Multi Subnet Listener is configured
• Synchronous Commit is configured

We are getting the good Autoseed performance for Database below 300 GB, But having a challenge while we add the heavily sized database 30 TB for Auto Seed. Estimated sync time was showing almost 11000 Hours to complete moreover after putting the Perfmon Counter we seen the Network Sendlog rate is very very low though there is a dedicated HRB (heartbeat) network.

I even tried the -T9567 Trace Flag also, but didn't see much difference.

Any advise on tuning the AutoSeed speed and Synchronous commit performance is highly appreciated.

Thanks
Momen