I do still use RPi-Monitor for temperature and load monitoring, but Cockpit does everything else (no temperature monitoring as then I could use just this one service). It will also install on any other running Linux computer.
Cockpit is easily accessible from a web browser so you can have a tab open per Raspberry Pi (or configure a single dashboard to access many Pi's) to quickly check log files, run software updates, drop to terminal prompt, manage user accounts, check what services are running or disabled, and graphs of CPU, memory, network and storage performance. It's all those essential things you should do but now don't have to SSH separately into every Raspberry Pi.
See Manage your Raspberry Pi with Cockpit
Last year, I wrote about using Cockpit to manage my Linux servers. It is a web-based tool that gives you a clean, powerful interface for managing multiple servers and their associated services and applications. It also eases regular day-to-day administrative tasks.