I believe this issue persists and is a cross-play issue between Switch and Kindle Fire OS. I will try to add bug replication steps so this ticket can be reopened.
Setup:
Playing on Nintendo Switch. Other device is Kindle Fire OS.
Both accounts using XBOX Live Login. Both confirmed as logged in both on device and logged in to online account.
1. Switch User Launches Minecraft. (1.16.201)
2. Switch User verify connected to XBOX Live
3. Switch User Load/create a multiplayer world on Nintendo Switch
4. Fire OS user launches minecraft (1.16.201).
5. Fire OS user Selects Play, then Select Friends Tab. No user games appear.
Important Notes:
1. If the Fire OS user creates the game, the Nintendo user can join.
2. This setup worked on earlier 1.16 builds. I believe it broke around the 1.16.100 or .200 updates.
I can confirm this issue persists. Additional notes that may be helpful.
I attempted the suggestions of turning off Cloud Save Auto Update. Like others, this did not resolve the issue.
This occurs for both Realms and non-Realms multi-player games.
This occurs while Switch is in handheld or docked.
This occurs while on WiFi or Ethernet connection.
This occurs regardless if there is one player or multiple players.
Cheers.