Weakened pelvis, ribs, collarbone, and all the future risk that entails. For that, alone, possibly cycling with its inherent risk of "bouncing" on the pavement (or worse) makes it too risky, given those injuries. Even when fully healed and you're as strong as you can get, there will always be the threat of those weakened areas succuming with another fall (if one occurs).

Might do a 3-wheeled recumbent or tricycle, for the change in stability and reduction in fall risk. Big change from a traditional bike, of course. But it would keep you in the activity and "out there" where you love it.

Might do walking and trails. Ruck marches, if you're up for pushing a bit. Keeps you outside, at least.

At a gym, for the cardio and general fitness there's always swimming and rowing. In addition to the resistance exercise you're doing in order to get strong again, which I'd imagine you're planning on continuing once "recovery" is about as complete as it can get. Sixty-four years of age, and all.

Good luck on your continued recovery. Looks like everything is going reasonably well.