Smart lock retrofit

I have an antique style door lock that a thumb lock on the inside.

Similar to this:
EuroProfile-cylinder-thumbturn_lrg

Does anyone know of a smart lock option that fits over the thumb turn? All our external locks are keyed the same so I don’t really want to change the cylinder.

TIA

You can get a new cylinder to match your existing key. Any specialist service can do that.

I’m looking for options that dont involve that, if they even exist.

It works and looks like a euro cylinder, but it isn’t actually one. It’s an antique style lock.

Plan b is fit a deadbolt and an August (or similar)

Well, if the lock and the key(hole) looks like the picture above, it should be no problem at all to get a cylinder that works on your current key. I would be cheaper as well as oppose to your plan ‘B’.

I clarified my original post. There’s no actual cylinder in the lock. The picture is to illustrate the thumb turn specifically.