GB wrote:

I'm a huge fan of 1strike.
https://www.amazon.co.uk/Everbuild-O.../dp/B001326TJA

It says 'no sanding'. I'm not convinced about that, but you do just bung
it in the hole, and it stays put without sagging.

I like it too, rake out the hole, fill it once relatively roughly as
deep as it takes in one go, give it an hour or two, tamp it down firmly
by thumb, give it another hour or two, then re-fill it level with a
filling knife, 24 hours to properly dry, minimal sanding and never had
the cracks open up again.