I am not a fitness expert, just an old guy who continues to bike and stay fit. During the pandemic, I have started to do the 7 Minute routine. I follow this one and it can be done in your home with your furniture, stairs, etc. But for the most part, you just need a mat or carpet floor. This will get your muscles back in shape. I would do it 5 times+ per week.
As for biking, just do it. As you lose weight and feel stronger, add distance. You have biked before and 61 is not old, if you are in a bit of shape. Since you have bike computed, I would get back to that as soon as possible. No matter how far you live from your business, bike part of the way as soon as you make this commitment. For example, if work is 10 miles from home, drive 7 with your bike and bike the last 3. Add distance each week. Why lose that day? And why drive a car, gain 40 pounds and feel you are out of shape when the biggest issue is likely your motor vehicle.

Good luck. Remember this is fitness season. Everyone becomes committed in December. Keep that fitness desire alive!