Each vendor will stick to its own DACs, AOCs, transceivers etc. Aruba is no exception. Unfortunately the only supported way to connect equipment from different vendors is to use Aruba transceivers on Aruba side, Sonicwall's transceivers on FW side and optical cable connecting both transceivers.
So for your question "if there is a DAC or twinax available that will work on both appliances" the answer will be "there is no officially supported by Aruba third party DACs".
Aruba 8325 supports following QSFP+ transceivers, DACs and AOCs:
Aruba 40G QSFP+ LC ER4 40km SMF Transceiver Q9G82A
HPE X142 40G QSFP+ MPO SR4 Transceiver JH231A
HPE X142 40G QSFP+ LC LR4 SM Transceiver JH232A
HPE X142 40G QSFP+ MPO eSR4 300M Transceiver JH233A
Aruba 40G QSFP+ LC Bidirectional 150m MMF 2-strand Transceiver JL308A
HPE X242 40G QSFP+ to QSFP+ 1m Direct Attach Copper Cable JH234A
HPE X242 40G QSFP+ to QSFP+ 3m Direct Attach Copper Cable JH235A
HPE X242 40G QSFP+ to QSFP+ 5m Direct Attach Copper Cable JH236A
Aruba 40G QSFP+ to QSFP+ 7m Active Optical Cable R0Z22A
Aruba 40G QSFP+ to QSFP+ 15m Active Optical Cable R0Z23A
Aruba 40G QSFP+ to QSFP+ 30m Active Optical Cable R0Z24A
HPE BladeSystem c-Class 40G QSFP+ to 4x10G SFP+ 3m Direct Attach Copper Splitter Cable 721064-B21
Regarding your question "Is there any thing on the Aruba 8325 or the Sonicwall NSa 6700 that could be disabled to allow the other vendors DAC to work?" - you can still try unsupported transceivers in Aruba 8325, however you do it on your own risk with no support for this configuration from Aruba TAC:
So will a Sonicwall DAC work flawlessly (or work at all) on Aruba switch? No idea, but you can try. But if you want to stay on the "light side of the force" ;-) this is the way - "I have to use different vendor specific fiber modules and a MPO fiber patch cable". Thus in case such connection goes wrong both vendors will be left with the only target to blame - the cable :-D
Hope it helps!
Sent: May 03, 2023 01:10 PM
Subject: 40G QSFP+ DAC compatibility between different vendors
I am needing to connect my Sonicwall NSa 6700 to my two Aruba 8325 core switches VIA a 40G QSFP+ lag. Do you know if there is a DAC or twinax available that will work on both appliances or would I have to use different vendor specific fiber modules and a MPO fiber patch cable? Is there any thing on the Aruba 8325 or the Sonicwall NSa 6700 that could be disabled to allow the other vendors DAC to work?