Short description:
If I try to join a LAN game (hosted by Windows 10 version), the game only shows up in the Friends list if I use a MS account with XBox live Gold subscription.

Reproduce:
1) Start a game on Windows 10

2) Log into xbox one and start Minecraft (account without Gold or Gamepass)

3) Go to Friends tab

4) Game does not show up

5) Make the console a home console of an account with Gold subscription

6) Repeat steps 1-3

7) Game shows up and can be joined

Notes:

I tried this with two non-Gold accounts. Both showed the same behaviour.

The xbox can host a LAN game without Gold subscription just fine.

See also: MCPE-35168 and MCPE-54655