Like in the good old days – a random collection of usefull sites …
Azure Commandline: https://cmd.ms
MS Portals: Administrator Portals | Microsoft Portals (msportals.io)
M365 Licensing: Home | M365 Maps
Exchange:
Exchange Prerequisites: Exchange Server prerequisites, Exchange 2019 system requirements, Exchange SE system requirements, Exchange 2019 requirements, Exchange SE requirements | Microsoft Learn
Build Number: Exchange Server build numbers and release dates | Microsoft Learn
Support Matrix: Exchange Server supportability matrix | Microsoft Learn
to be continued …