Another option for engineering is work on alternative foods for catastrophes—there are many engineering projects listed here. You could volunteer/intern at ALLFED even as an undergrad.
This is a cool list, thanks for compiling it! For ease of others viewing, I’ll just list a couple that seemed most in the direction of the “hard” physics-based engineering as stated in the original comment:
“7. Open source leaf grinder for leaf protein extract from tree/crop leaves. Leaf protein has been produced at the household and industrial scale. - (S)
10. Work out how to recover industry as quickly as possible, e.g. focusing on making replacement parts destroyed by EMP (and estimate time of recovery). - (E)
16. Quantify the impact on energy/electricity production of nuclear winter, particularly solar, wind, and hydroelectricity. – (S)
25. Develop open source wood chipper. - (S)
27. Develop an open source shortwave (HAM) radio system (two way or just receiver). - (E)”