earliest release year

[Mayibongwe]

I'm late to the game, but how do I install this plugin?

We do have some Picard users here - maybe one of them will jump in to help.
But coming from myself who's never used it, I would have suggested that you would have better luck asking this at their forum.

[hiccup]

I'm late to the game, but how do I install this plugin? https://github.com/avh4/picard-recordingdate - when I install it says not compatible with my version of picard, I am using Version 2.12.3

I just tried it by doing a clean install of Picard Portable 2.12.3, and the plugin installed without any issue.
So my guess is that you are doing something wrong.

Did you do:
Options > Plugins > Install Plugin…
and then navigate to the downloaded recordingdate.zip file?