Had a stroke 12 years ago when I was 19 (before any PED use). It’ll be important for him to figure out if it was caused by a clot or by a bleed. These are two very different scenarios that he’ll have to think about.
Even if somebody is perfectly healthy, the doctor will be 100% against any drug use, especially in this context. I would tell him to get in touch with an endocrinologist or HRT doctor who is more specialized in this field.
Personally, I was lucky to bounce back with little to no lasting effects. So it is possible for him.
That part of his life may not be over, but like others have said, I’d probably stick to TRT and prioritize keeping health markers in range for awhile.