First time starting server with the dynmap plugin generates error:
>.... [16:15:42 ERROR]: [dynmap] Error reading plugins/dynmap/markers.yml

Other information:

• Paper version git-Paper-143 (MC: 1.15.2) (Implementing API version 1.15.2-R0.1-SNAPSHOT
• Dynmap v3.1-beta-2

Good news! This feature request was implemented in d535489 and has been in Dynmap releases 3.3beta2+

Can you pastebin your markers.yml file

Markers.yml pastebin: https://pastebin.com/rkJwZbcR

Does this only ever happens on a fresh server with a new installation of dynmap?

Or does this error happen every time you start the server?

It does produce the error only with a fresh installation of dynmap!

Steps to reproduce:

1. Use paper 1.16.1 & setup the server
2. Stop server & drag Dynmap v3.1-beta-2 into plugins
3. Start server and you'll see the error message

Just confirmed a second time on another server without dynmap.

>.... [00:33:20 ERROR]: [dynmap] Error reading plugins/dynmap/markers.yml

I honestly think this is intended behaviour. The plugin doesn't find a markers.yml (because its a fresh install) which promts the code to create one from the default template. This first-run error should probably read differently but I think it was just a quick fix and reusing code to generate the config on the first run.

As server administrator it is confusing, I suggest to give a clearer message.