I have been divorced for 32 years, and we divided our assets in 2018. At that time, I became the sole owner of the house. Today, I am selling it. Will I be liable for capital gains tax?

Yes. The seller is exempt from capital gains tax when selling a property that has been owned for more than 30 years (BOI-RFPI-PVI-20-20 §§60 and 70).
In your case, the holding period must be calculated in two separate parts:

You became the owner of half of the property more than 30 years ago. You will not pay tax on that share.
However, you acquired the second half of the property upon division in 2018. You will be liable for tax on that portion (BOI-RFPI-PVI-20-10-20-10 §280).