right after connecting to my workstation it says: “herdr is not installed on this host” while it clearly is. Running it in shell directly works, but it’s impossible to scroll inside herdr session like that. What exactly should I pay 99 for?

Are you running fish shell? If so, this was fixed and waiting on AppStore approval to release it.

Let me remind you that this is/was my ironclad setup. It should work for others, but may not due to preferential or not-my-machine technical reasons. The latter is solved by bug reports. Either way, there's a free trial and you pay nothing & shouldn't unless you like it.