The cartridge(Canon) in the image shown by elektryk is an integrated head type cartridge.
In this case, the head is in the cartridge, so the price of the printer itself is lower and the price of the cartridge is higher.
Yes, it is refillable.
A hole is drilled in the top of the cartridge and about 10mL is injected with a dropper.
Ink should be fine as long as it is from Canon. Recently, a cartridge-less, bottle-type ink that can be set directly into the printer is available. I think it is also possible to suck it.
If PG-575/576 is the same as 310/311, this ink does not have a chip that records the remaining ink level.
Therefore, even if the printer is determined to be out of ink, it can continue to be used as is. In that case, the remaining ink level indicator should be grayed out on the computer.
This is in Japan.

p.s.
In Japan, canon used to manufacture this type of printer, iP2700 I think.
Interestingly, the price of the printer itself was cheaper than the price of the cartridges, which led to an interesting phenomenon: people didn't buy cartridges and replaced the printer when the ink ran out. For a while, the junk stores were flooded with iP2700s. At $5.