Been having this problem for a while now, not sure what's going on.  The last real achievements I've earned were on May 19th, 2019. I've posted in multiple places for support with no luck, so I've decided to file a bug report.  I think I've done everything I possibly can to try and work around the issue.

• Nintendo and Xbox Live accounts are linked and connected
• I have received achievements in the past
• World has never been in creative mode and there's no warning banner on any of the worlds saying you cannot earn achievements on this world
• Multiple worlds have been tested including newly spawned worlds
• Achievements that are having issues include the time played one, smelting iron, and wearing a suit of iron armour
• I've deleted the game data and reinstalled
• I've tried obtaining achievements on a second Switch with no luck
• I've done the task to trigger the achievement and let the device sit for 10-15 minutes with nothing popping

Other posts (at the time of filing this ticket they all have 0 replies):

• https://www.reddit.com/r/Minecraft/comments/cc3dv7/nintendo_switch_xbox_achievements_are_not/
• https://www.reddit.com/r/Minecraft/comments/cc3dv7/nintendo_switch_xbox_achievements_are_not/ 
• https://www.reddit.com/r/NintendoSwitch/comments/c9uo5e/minecraft_achievements_not_unlocking/
• https://www.minecraftforum.net/forums/support/minecraft-bedrock-support/2971135-switch-xbox-live-achievements-are-not-unlocking
• https://www.trueachievements.com/forum/viewthread.aspx?tid=1114375