Is there a change history for DJIFly versions? I would like to choose the best version for the mini 2, without unnecessary additions for newer drones.

I fly a mini 2 using Fly app versions 1.3, 1.4.8 and I think 1.5.4  something, different phones. That I know of, there is no clear history, in the sense  that you probably mean,  most version notes seem to contain "to fix xyz" statements and or "to improve abc" i.e. very little useful information.
The only one where I saw something I was interested in added was perhaps the 1.5.4 where I think it became possible to either change the joystick EXP setting or perhaps the something like drone yaw rates, as you may have gathered it is a rather vague recollection so I haven't used the feature much lol

BTW this all applies to ONLY android, if you use apple stuff I think you are stuck with the current version.
If you find a 'good' history, PLEASE post a link to it.

Try v1.5.10, most stable for mini 2 version to me.

Agree, this is the last version with mini 2 support. From version 1.6 mini 3 pro support starts. And from 1.7 for Avata.I found such a list in the DJI Fly app store IOS.

New corrected and supplemented list of changes.

Those are a darn site more detailed than anything I have seen for Android. Is that due to Apple saying YOU MUST give details of what changes have been made? If so, well done for Apple!

Mini 2 release notes
Link tag does not work :-(
https://dl.djicdn.com/downloads/DJI_Mini_2/20230331/DJI_Mini_2_Release_Notes_EN.pdf

New corrected and supplemented list of changes.