In ExpressionEngine 6 we added a new check, for broken tags etc. Which I'm guessing is why these have surfaced during the EE 6 upgrade.
The following is a bit of a breakdown of the tags mentioned above.
I believe this add-on was removed starting in version 2.0 https://docs.expressionengine.com/v2/installation/version_notes_2.0.html
Removed in version 3.0 https://docs.expressionengine.com/v3/about/changelog.html
Replaced with Emoji module in Version 4 https://docs.expressionengine.com/v4/installation/version_notes_4.0.0.html#emoticon-module
So some of these (emoticon) can be updated, others likely removed. My guess is that the functionality around these tags hasn't been working as intended for a while, or the add-ons we manually updated to support the newer versions of ExpressionEngine.