Combat Anoms in Null pay reasonably.
You get something like a Serpentis Prison Camp and you get:
the 21st overseer’s personal effects - 80m guaranteed*
The bounties from all the ships multiplied by the Bounty Modifier - in the order of another 40 to 60m depending on the system (modifiers may vary)
Then the loot can be quite reasonable, especially if a shadow ship spawns, as these can carry loot worth up to about 250m depending on the ship (I find smaller ships to be more likely to have a hugh value object, battleships often let me down)
So I would generally try to look for one or two of these of an evening, sometimes three, and you can clear these comfortably but slowly in a RNI, or faster but less comfortably in a Golem (bastion mode in null will stop you falling asleep!)
If Alpha, you can do these in a Barghest, which is my favourite Alpha-Friendly BS.
Other real easy ones are Rally Points, Hubs and Military Complexes, but these aren’t as nice as the prison camp in terms of payout, but are generally quicker to do (fewer rooms)
*The 80m is only guaranteed if you sell it specifically to Concord at one of a small amount of stations, but if you just swing by Jita once a week in a Viator and dump everything then you’ll get around 67-73m for it most of the time.
Edit: Did something called a “Paramilitary Complext” the other night, took about an hour, around 500m isk all totalled. There were three shadow spawns in it which EvE University suggests is normal. Load up on as many of those as you can, they’re easy.