Researchers have reported neutron detection but these results have not been reproduced and some scientists have attributed this detection to 'noise'. Bubbles are tiny they have very small amount of gas in them so detecting that is not exactly straightforward... I think

for example a in a 1um radius bubble the total mass of gas would be ~ 10^-18kg.

Personally I doubt fusion occurs inside bubbles. Even if we take the highest reported temp 30000K that's way below what's required for fusion.

Also bubble literature is full of fantastic claims—one that comes to mind is assertion that pressures of around 10Gpa can be generated which seems highly improbable because that's likely to induce phase change in the fluid.

However it's quite possible that I'm wrong. Because bubble science keeps on throwing new surprises.