is there any How-To available which explains in detail how to setup an own block explorer?
I see people already have you some hints. I will give you one more: I've made myself a step-by-step tutorial for installing and configuring Electrum Server (electrs) and also Blockchain Explorer (rpc-btc-explorer). It can be done on Windows (by installing WSL and then Debian) or directly under a Linux. Bitcoin + Electrum server + Block explorer under Windows (with WSL and Debian). Good luck!