Sure! I’m not too well-versed in this topic, but here’s a gist of it:
First, it’s a very old idea, somewhere from 1920s I think. Proposed as a possible solution way before we found out about the expansion.
One of the main issues is it violates conservation of energy, since in this hypothesis the photons lose energy en route, but there’s still no viable mechanism to absorb or account for that energy. It also doesn’t explain cosmic background radiation, while other theories explain it quite well.
Then there’s blur. If the light loses energy on interactions and all that, the photons should scatter and blur the image. That doesn’t happen.
And then there’s this time-dilation effect. When you look at supernovae at different distances, their explosions “run” at different paces, with further ones exploding slower. In LCDM model that’s easily explained by the light being stretched because of the expansion, and that’s what causes slower “runtime”. With TL’s predictions that shouldn’t happen at all, yet it’s an observable effect.
And there are probably more discrepancies that I can’t remember off the top of my head.