user-1: Bind local IP (Node 1)
bitcoind -regtest=1 -port=18333 -bind=192.168.150.110

Logs:
2021-09-01T13:14:16Z Bound to 192.168.150.110:18333
2021-09-01T13:14:16Z Bound to 127.0.0.1:18445

Trying to add it in peers.dat (Node 2)
bitcoin-cli addpeeraddress "192.168.150.110" 18333
{
  "success": false
}

Why does it return false?

user208: peers.dat (and the associated RPCs) are for the automatic connection mechanism, which includes relaying to other nodes.
You're adding an address that is not globally routable (it's a LAN IP). It cannot be inserted into the automatic connection database, because it cannot be relayed to other peers.
If you want a connection to it, use the manual connection mechanism (i.e., addnode RPC, or -addnode or -connect options).

-1: <p>Bind local IP (Node 1)</p>
<pre><code>bitcoind -regtest=1 -port=18333 -bind=192.168.150.110
</code></pre>
<p>Logs:</p>
<pre><code>2021-09-01T13:14:16Z Bound to 192.168.150.110:18333
2021-09-01T13:14:16Z Bound to 127.0.0.1:18445
</code></pre>
<p>Trying to add it in peers.dat (Node 2)</p>
<pre><code>bitcoin-cli addpeeraddress &quot;192.168.150.110&quot; 18333
{
  &quot;success&quot;: false
}
</code></pre>
<p>Why does it return <code>false</code>?</p>
 208: <p>peers.dat (and the associated RPCs) are for the automatic connection mechanism, which includes relaying to other nodes.</p>
<p>You're adding an address that is not globally routable (it's a LAN IP). It cannot be inserted into the automatic connection database, because it cannot be relayed to other peers.</p>
<p>If you want a connection to it, use the manual connection mechanism (i.e., <code>addnode</code> RPC, or <code>-addnode</code> or <code>-connect</code> options).</p>
