I travel with the following:
Canon R5 + at least 3 lenses, batteries, etc...
Ikelite housing & ports (including 8" dome)
2x Ikelite DS230 strobes plus 2 spare battery packs
Arms, clamps, sync cables, spare parts, etc...
Collapsible boat bag for the camera rig
I have a nice camera backpack (WANDRD PRVKE 21 liter) that easily holds my camera body with a lens on it, 2 other large lenses, plus my laptop, batteries, cables, portable hard drive, and any other electronic stuff I may need. That gets carried on and goes under my seat. It's heavy, likely over many carry on weight limits, but explaining that it's like $10K worth of camera gear usually gets rid of any pressure. Or sometimes I'll throw my laptop in my checked bag if they're being a pain about it.
Then as one of my checked bags I have a Pelican case, specifically a 1620. It's got the foam inserts you can cut out to securely hold whatever, and it easily holds my camera housing, all ports/extensions, strobes, strobe batteries, sync cords, and a couple small plastic boxes full of o rings, lube, spare parts, and other small housing accessories. The whole thing weighs in at around 45 pounds packed, so no issues checking it anywhere. It's also basically indestructible and they could play rugby with it on the tarmac and it wouldn't hurt anything inside.
Then I put my big mesh bag full of clamps and strobe arms along with the boat bag in with my dive gear in whatever bag or suitcase I'm checking to carry my BCD, fins, wetsuit, etc...
But yeah, no way to avoid two checked bags when travelling with a substantial camera rig. I've heard of people carrying on fully assembled rigs in boat/cooler bags and putting them in the overhead bin as a carryon, but I'd never risk that. That's like $10-15K worth of hardware that people can bang, drop or whatever. Not to mention it'd be way over any carry on weight limit especially internationally. I just pay a little extra to check the pelican case. It's a drop in the bucket compared to the cost of all the gear. I haven't had any problems going wherever I need to go with 2 checked bags so far, even on tiny little twin otters to remote islands.