This specific paper doesn’t seem to mention it, but the other common bacteria used for this purpose is Saccharomyces cerevisia (AKA Baker’s Yeast).
Before this, people who needed insulin were forced to use pig or cow insulin (which wasn’t perfectly identical to human insulin, but was better than nothing), or rely on insulin donations from other humans.
https://www.sciencedirect.com/science/article/pii/S1046592818305862
ref - https://www.reddit.com/r/todayilearned/comments/dsyg1r/til_that_the_most_common_way_to_synthesize_human/
origin - https://www.pipiscrew.com/?p=15678 most-common-way-to-synthesize-human-insulin-for-medical-purposes-uses-a-harmless-strain-of-genetically-modified-e-coli-bacteria