What is the ruling on trimming the beard or shaving it completely, knowing that shaving it completely is unlawful, and that a long beard collects dirt due to the nature of one's work?

Acting upon thenah encompasses both outward and inward aspects. The matter of letting the beard grow and refraining from shaving it is established in the Sunnah, and the majority of scholars do not permit shaving it. If the questioner is bothered by the length of his beard due to the nature of his work, which accumulates dirt, then he has an excuse to trim it without shaving it. He should not remove most of it to the extent that it resembles shaving; rather, he should leave enough to cover the jawbones. This aligns with the view of some scholars regarding the meaning of "إعفاء" (letting grow).