Hi,
this is for the minority of people who don't use steam for various reason.
Since 95% of all mods are released at the workshop and only a few of the mod author's provide non-steam download link it was sometimes frustrating to get interesting mods.
I discoved some websites which allow to download workshop mods.
http://steamworkshop.download/ (bad expierence since i rarely got he latest version of the mod even after tynan set some flag)
https://steamworkshopdownloader.io/ (worked well, but sometimes overrun and you still need to copy/unzip the mod manualy)
The author of RimPy the offline mod manager add the integration of SteamCMD, a commandline tool from valve itself. SteamCMD allow you to download workshop entries with an anonymous login, so you don't need a steam account.
https://steamcommunity.com/sharedfiles/filedetails/?id=1847679158Direct download at the steam description.
Get SteamCMD
https://developer.valvesoftware.com/wiki/SteamCMD
Install SteamCMD
Install RimPy
Setup the path's, without using steam let the path for steam mod's empty.
Under Downloader, you can setup SteamCMD (button is down left).RimPy download and install SteamCMD by it own now. !First use the browser, to select a workshop mod.
Then use "Add mod to download list" and continue browsing and adding.
"Check for updates", would check for updates from workshop mods and add them to the download list
To remove entries from the download list, double click at them.
Then use "Download" to activate steamCMD and download the mod's from the download list.
They auto. get copied to the Mods folder.
It can't happen that the download with SteamCMD don't work, i encounter that problem serveral times so far.
But i think it is because of your anonymous login and registered user get prefered.
I suggest that you try it again a few hours laters.