> bunch of organisations that just probe the entire IPv4 range on a regular basis

Yep, #1 source of junk traffic, in my experience. I set those prefixes go right into nullroute on every server I set up:

https://raw.githubusercontent.com/UninvitedActivity/Uninvite...

#2 are IP ranges of Azure, DO, OVH, vultr, etc... A bit harder to block those outright.