There are a few interesting mechanisms of bacterial resistance. They don’t carry anything with them but genetics, so it’s hard to say it’s Not “always ... mutation”, but the genetic pathways have some interesting variety. You can form bio films, you can form spores, you can have Cell Wall materials that are less target-able by Cell-wall-targeting abx, you can build your own enzymes to degrade abx, you can build pumps to actively pump abx back out of the Cell, you can trap the abx between your cell membrane and your cell wall so that your defensive enzymes have a much higher effective concentration, etc. That’s not even getting into the abx that target transcription and translation, rather than just Cell wall destroyers.

I think the traditional mental model is “evolve a slightly different target molecule so abx can’t target them anymore,” which yeah, vastly understated the complexity.