Probably lilac blight.

A lot of that going around.

Call your county extension office and ask for advice.

They might want a sample to examine and test pathologically.

Ah, I don't think that's it. Two years in a row, other lilacs nearby not doing this.

Any other experienced opinions? Appreciate it!

There are a couple other diseases in addition to bacterial blight that can affect lilacs - Septoria and Pseudocercospora - see this link: Lamentable Lilac Leaf diseases (Purdue Landscape Report)

If there is leaf curling or cupping, unfavorable soil conditions or herbicide injury may be the cause.

Well the leaves es are curling as they are quickly browning completely. The curling is following the beginning of browning/drying dying of the leaves for the season. It comes back strong in the spring, but this is new for September-November the past two years. There is one branch that once broke in an ice storm that I nut/bolted together where perhaps there is a source of disease ultimately for the whole plant. That area has gradually withered away in that bolted area one season at a time and is close to the earliest branch/area to start browning. So, I'll prune that branch completely in February and treat the whole plant in early May like I read via google Lilac disease search. Thanks...

You didn't mention your location. The mid Atlantic had a severe drought last fall and now a moderate drought. I'm wondering if weather is exacerbating the usual lilac powdery mildew.