Uptime Kuma is the most intuitive and easy service monitoring tool i have used, It supports 2FA authentication and can monitor any specified client or TCP port with many configurable options such as notifications and delay
Yacht is very similar to Portainer. It allows creation and management through its web UI. some of the cool added bonuses that it can do, it supports authentication, templates to quickly boot up docker containers, and manageable networking configuration directly from the UI