Assuming that your fracture was a simple transverse fracture w/o a lot of joint surface comminution, most surgeons would probably just put you in a sling for about a week to let the skin and soft tissues heal and then start some early gentle passive range of motion.
I’d probably be okay w/ allowing bike trainer rides (where you don’t use the affected arm) as soon as the incision is dry and no longer draining (48-72 hrs). Riding in the aerobars is going to cause less pull of the triceps and resultant stress on the repair site than riding on the hood or drops. I think that would be reasonable to start in the 4-6 wk time frame. Running probably at 4-6 wks too.
Riding on the hoods or drops is the last thing I’d feel comfortable with because it will stress the repair. Probably more like 6-8 wks.
The biggest issue with these injuries is lack of a few degrees terminal extension (ie. not being able to get the elbow straightened out all the way), so that will be something to work on. Also, symptomatic hardware is not uncommon with olecranon fractures. Placing the aerobar pads beneath the proximal forearms will be better than having them beneath the elbow if that is what you did previously.