simple asf, i've done the math, all that is required is 450 giga tonnes of nitrous oxide ( a simple molecule to manufacture using in situ ammonia and oxygen at Europa), the total energy debt would be settled by about 10% of the world's energy production for 26 days, Io a nearby moon can supply this very simply using a literal lighting pole at its pole from the flux tube of Jupiter and io generating 2 terrajoules a second in electrical current. this could very simply be beamed to europa using a microwave antenna and a rectifier with a conversion efficiency rate of 20-80% ( 4 months worst case scenario to settle energy debt). this would raise the average temp of Europa to ~15 Celsius causing the ice crust to begin to melt. Europa's ice is chockablock filled with oxygen caused by billions of years of radiolytic water decay, each cubic meter of ice melted is 1.7-7.5% trapped oxygen clathrate by mass meaning just the top 300 meters of ice crust would release at the lowest estimate 5100kg's of oxygen per square meter, given the lower gravity of Europa 7.46x weaker than earth thats 0.068 bars of pressure which is above the Armstrong limit 0.061 bars ( point your blood boils), and thats with the MINIMUM pressure of just the top 300 meters, the pressure could be as high as 0.3 bars of oxygen WHICH IS FUCKING BREATHABLE. within a decade or 2 the top kilometre should have thawed at which point the atmosphere will definitely be breathable.

p.s. in before the illiterate niggers " hur dur its too small to have a atmosphere" it would take 3000 ish years for just the atmosphere from the top 300 meters of melt to be blown away based on the MINIMUM pressure, the full oxygen inventory of the crust would last hundreds of thousands of years not even including accumulation of oxygen caused by water decay in the upper atmosphere ( Europa has more than enough water for MILLIONS of years)