The department of education has the simple authority to forgive loans, a process they're using right now (with a huge bureaucratic overhead of means testing, using loan servicers, etc).
For whatever reason they initially decided to try and use the heroes act instead, after declaring that the pandemic was 'over'. So of course the Supreme Court struck it down.
They could've just told the education secretary to forgive everyone's loans from the start. Or set the interest rates to 0% for everyone (as it's really the compound interest that's killing everyone).