I could not find the Delogo filter in my German version. I have 2.7 on an Imac with 10.13.6. Any ideas?
There are no current official High Sierra-compatible Avidemux builds. The problem is that required libraries from Homebrew are not backward-compatible, so while declaring High Sierra as deployment target allows the application built on Catalina to run on High Sierra, it is half-broken as all plugins depending on bundled Homebrew libraries cannot be loaded. AFAIK, Homebrew doesn't provide an easy way (or any way at all) to have a (parallel) installation on Catalina with High Sierra as deployment target.
That said, if you need Avidemux, you have the choice either to upgrade your Mac at least to Catalina or to build Avidemux yourself. The latter is basically not difficult at all on macOS, but the Xcode application from Apple occupies an insane amount of disk space (~50 GiB) and a sufficient support from Homebrew cannot be taken for granted (they call it "best effort" support). Obviously, the build on High Sierra hasn't been tested since I updated my MBP to Mojave.