"Dave" is actually pretty successful as a free-to-air/basic cable channel. It built itself on things like repeats of Top Gear and QI (and other comedy panel shows). These days it commissions lots of new bits and pieces like the recent feature length Red Dwarf (Dave took it over a few years back and commissioned a few new series), and the very funny Taskmaster (which didn't work out for Comedy Central with a one-and-done season presented by Reggie Watts). In the UK, Taskmaster, made by the same production company that makes Last Week Tonight, has been subject to a big money transfer to Channel 4 - once they can make it anyway. Taskmaster is still continuing though as strange YouTube series with members of the public - very family oriented. And very creative and funny.
I digress.
Also of note is that Dave is 100% owned by the BBC (via BBC Studios, the BBC's commercial arm). And yes, it is ad-funded.
Adam