I said that had heard of him in response to your saying the same. Paganini and Beethoven apparently had a falling out over something. Rossini wanted to meet Beethoven and after meeting him, Beethoven complemented his opera buffa abilities and recommended he stick with that. Donezetti was active in Italy and later gained fame across Europe, traveling all around the region. Much of this was at the same time as Beethoven. While I cannot prove that they met, it is almost inconceivable that Donezetti hadn’t heard of Beethoven.

Furthermore, your criteria was for an orchestral composer IIRC. Each of the composers you chose were not known for this. Of course each did use the orchestra, but their use was as an accompanying element to highlight either solo works or operas. Yeah, yeah, I know they wrote small pieces for orchestra alone, but those were not their primary focus. Additionally, Beethoven was not an opera composer other than Fidelio.