-Mod Help

  I use the term “mod” loosely in this instance, since what I do barely qualifies.  Anyhow, what do people use to modify *.lbm texture files?  I did a few modifications at some point in the past but now I’m having issues with the files.  I generally use Paint.Net for most things but in spite of the many plugins, Paint.Net remains useless.  Previously I used Corel Paintshop Pro 2020…at least I believe that to be the case, but Corel isn’t working now.  I’ve also got Adobe Photoshop 2022, and that has failed to produce results as well.  I realize I’m trying to alter game files from a hundred generations ago so issues are to be expected, but this is a little frustrating.  Adobe will save in the .lbm format but the game doesn’t read them.  Corel won’t save in .lbm, but the Amiga .iff format seems okay.  And Paint.Net is completely useless.
     I feel like I’m missing something obvious and relatively simple that time drove from my feeble brain.