Nalirifox was approved by the FDA last year. It's basically a reformulation of Folfirinox using a newer version of irinotecan called Onivyde (liposomal irinotecan).
https://www.fda.gov/drugs/resources-information-approved-drugs/fda-approves-irinotecan-liposome-first-line-treatment-metastatic-pancreatic-adenocarcinoma
I've had two oncologists recommend this as a possible next step if I develop resistance to Gem+Abrax+Cisplatin, but I don't think I'll ever go that route unless a head-to-head study shows Nalirifox being vastly superior to Folfirinox. I only had a so-so response to Folfirinox before my Whipple, and my gut feeling is that changing one ingredient won't buy me a response worth all the side effects. Everyone is different and I have zero medical training, but that's my thought process.

Outside of those, you're basically looking at clinical trials, or previously approved drugs used off-label. PARP inhibitors have been approved for other cancers, and have tested well in pancreatic patients with BRCA1, BRCA2, and PALB mutations. Olaparib (Lynparza) is one PARP inhibitor with approval for other cancers, making it "legal" for off-label use in pancreatic cancer (as I understand the law).

PARP inhibitors may eventually prove effective in patients with other mutations like ATM, but not yet in large studies. However, I did find one encouraging case report of a gastric cancer patient with an ATM mutation treated with a combination therapy of Olaparib added to nivolumab with fluorouracil and docetaxel. After accumulation of side effects, patient was transitioned to Olaparib monotherapy and continues to do well.
https://pmc.ncbi.nlm.nih.gov/articles/PMC10953106/
You're going to need an oncologist willing to think outside the box, go out on a limb, etc... I hope you do and I wish you well!