we are pleased to tell you that we created an app called "Netman" which should meet all your requirements in terms of network inventory, planning and monitoring. It is quite easy to use, has 2 languages (polish and english). Main features in terms of monitoring include embedded syslog server, snmp and ping monitoring, notifications sent by Telegram bot.
Currently, we are giving away 2-months free license keys to everyone interested. If you are interested, you can get it by downloading netman from our website and filing simple form (company name and e-mail addr) in DOWNLOAD section.
If you are interested, please visit our website: http://wisoft.pl/en
There is also Youtube channel showing Netman and its features: https://www.youtube.com/channel/UCk7_cAaEIY_v-o_Hideun0w
Also, docs (still in polish, english version is WIP) at http://wisoft.pl/docs-pl