My game crashes when the 2nd Gorg fleet arrives in the mission. I searched a bit and saw that people have that problem when they put their own ships near the wormhole, and that it's supposed to be ok if you keep your distance. However, when the Noah fleet arrives they decimate me completely with their missiles, and the only tactic that worked great for me was taking them on just as they pop out of the wormhole.

So is there a workaround for this crash? And if not, anyone has a suggestion on how to handle the Noah fleet without closing the distance on them?

I had exactly the same problem. That crash seems to only happen if you are near the wormhole when the 3rd or 4th wave arrives (I wonder if its just too many ships near the wormhole at once?)

So I blockaded the wormhole as normal (saving very regularly) then abandoned my position when the crash became inevitable. Then I used a bomber/gunship assault to weaken the remaining ships (focusing on destroying shields and engines so I could tackle isolated ships rather than fleets).

That strategy worked even with the crash

When I had the exact same problem in a recent replay, I assumed it was because of my meddling with the game, as i had done a bit of light modding, since I think I had played trough the game years ago without running in this particular problem (I distinctly remember having to restart several times until I could get out of solar system on the Angelwing without a crash though, what wasn't a problem this time at all).

So, I decided to... do worse, and dived in the scenario files. Long story short, I believe I sorta isolated the problem to a set of AI instructions for that fleet that, as far as I can tell, was intended to make them concentrate fire on our ships one at a time.

So...

...what I apparently had done, and what may or not be possibly a very crude and rude solution, as it seemed to get me try... in file:
\universe\missions\EPISODES\063_2_AIFleetControll.mach
I commented out line 243
//M:GetMachine("AIGorgFleet_a"):ChangeState(Hent, 0);

And lines 262 and 263
//SetDetected(Pickfirst(Fleet1L), #race_Mechanoid, 1);
//DetectEnable(Pickfirst(Fleet1L), #race_Mechanoid, 0);

(Changes, the added "//" in front in bold)

But I'm not really knowing what I'm doing there and someone with real understanding will probably tell I had broken something in a way that just accidentally got a workable workaround or this particular stuff might indeed be relevant only in light of my previous modest changes to same equipment stats.

Also somewhere on the way I ended up swapping first and second Gorg fleets but I think I reverted that for the final variant (and yes if I believe I remember it right the second fleet is called first and Fleet_a in the files, but it seems to have been last September, so not yesterday, lol; if not line 253 could be the other relevant).

If it does what I think it does it simply reverts them to default behavior disabling specific instructions for the occasion. They wasn't like sitting there doing nothing, even if potentially dumber and less cunning as they were supposed to be.

Ah, and for those particular of changes to go on effect you would need to go into the mission anew from before the debriefing.