I have an outdoor meter main panel (Eaton MBE2040B200BTS) with the following circuits: 15A and 20A septic, a 30A 120v RV hookup, a 20A outdoor utility outlet, and an Eaton BRS225 Main Lug Kit that feeds my 200A indoor manufactured home panel. I want to put a generator hookup outside for backup power to keep emergency loads like the septic and refrigerator on. I understand the generator won't handle my HVAC, Water Heater, Dryer, or Range so those breakers will be turned off in the house before starting the generator. I plan to use a double pole 30A breaker and this interlock kit. Can I mount an inlet like this directly into the bottom or the side of the meter main panel and skip the additional inlet box and conduit? I have a hydraulic knockout kit with a 2.36" die to make a clean hole.
Not if it's outdoors
And the electric meter is on it, so I presume it's outdoors.
The reason is NEC requires a weatherproof cover. The same company makes those for $40 more... and you can connect them to the panel with a $3 offset nipple (which gives you 1 axis of freedom of movement to match it to surfaces).
You also have NEC 110.3(B) to contend with: "Use equipment according to labeling and instructions". That is notably applicable to your NEMA 3 rated enclosure, vis-a-vis where on the enclosure a knockout may be located. It also applies to the inlet. "use according to" means all uses are forbidden except the permitted ones.