I can get my entire m43 rig (housing, lenses, ports, domes and strobes) into this bag:
https://cabinmax.com/collections/backpacks-2/products/metz-44l-classic-colour-cabin-backpack?variant=34928638623910
I carry it on my back and make hefting >17kg look like it no big deal to avoid having it checked in. I'll be moving to a wheeled bag solution soon as I'm aging and don't want to slip a disk on my way to a destination!
I take my regs, computer, mask and other essentials in this:
https://cabinmax.com/collections/easyjet/products/anode-30l-45x36x20cm-easyjet-underseat-cabin-case?variant=40588605980838
I have 5 bags from Cabin Max and can't recommend them enough. You can shop by airline so you know the dimensions of the bags you are shopping for precisely meet the allowances. No brainer if you're based in the UK.