I realize you’re trying to solve an annoying notification but it is possible to install Monterey on your machine via community solutions such as the OpenCore Legacy Patcher( supported macs at link ). Mr. Macintosh, a well-known suppport site, has lengthy instructions and a detailed video. My 2009 MacBook runs Catalina just fine for basic computing using another hack from dosDude. There are caveats to this approach but it is an option for many. ymmv.