Welcome to the 50+ forum!

Here's the thing.

In the long run, unless you "love" bicycling, riding a bike for the cardiovascular exercise as the prime objective will get "old" very quickly, and the bike will finally end up hanging in the garage. So, try bicycling for a bit to see how you like it and how you want to ride before investing a lot of $$ in a "final" bike.

Also, the first bike one buys generally ends up being the bike that points you in the direction of the next bike that you want. Many in this forum (including me) have gone through this transition or even more. (It is called n+1). IOW, it is a process and not a destination purchase.

My suggestion is to get a nice hybrid. Brand is not generally an issue. They are all good. but, the LBS (local bike store) you buy it from IS. Generally you are buying a bike store, who will fit you on a bike, and the proper fit IS an issue. Also, a "road equipped" mtn bike can do very nicely.

JMHO

Have fun