So I installed the game via Windows and copied the game over to my 'dosgames' directory, but upon running it in native DOSBox I get a "Theme Hospital needs the CD to run" error. Any suggestions?

Yes. Open the hospital.cfg file in the game directory with a text editor and change the path in the INSTALL_PATH=... line to the one you are mounting the folder to in DOSBox.

I tried this a few different ways with a few different parsings, usually " .home/user/dosgames/hospital/ " and it just doesn't seem to see it. Am I missing anything?

Sorry, I didn't explain thoroughly. It's not the path of the directory you are mounting, it's he path of the game's directory as mounted in DOSBox that you need to enter there.

That file is not DOSBox's but of the game, and the game only knows the directories as they have been mounted, not as they are outside DOSBox.

For example, If you are mounting /home/user/dosgames as C:\ in DOSBox, with all it's subdirs as directories under C:\, then you need to enter C:\HOSPITAL in the configuration file.

That's all good as long as you keep the GOG installation complete, which of course does not make much sense if you want to have tens of games well ordered and ready to run, as I do, or if you are transferring the game files to a different OS, as the OP. In both cases, you take the actual game files and leave all other GOG files behind (usually excluding DOSBox config files as well).

And the OP's issue has nothing to do with the DOSBox config files. It's all simply due to the game base folder being named differently from the one set in the game's config file (which is originally C:\HOSP if I recall correctly). Even in Windows and having the full GOG install, if you rename that HOSP folder to something else, you will still get the same error as the OP.

GOGs hospital.cfg contain only c:\
If you move installed game and remember launch parameter - game work from any folder from any OS. If you already change path in cfg - you must revert it back. In that case you probably can forgot about back slash. Path must look like this
=c:\
If you use own conf file "main"\"single" - with own custom AUTOEXEC section - you must change game cfg path to look like this
...\games\theme-hospital\ - again with backslash.

P.S. single conf file with AUTOEXEC section from GOG contain that text after [autoexec]
# Lines in this section will be run at startup.
@echo off
mount C ".."

c:
cls
HOSPITAL.EXE
exit

(two empty strings at the end)

That is for how the game is installed by GOG, mounting the game directly to C:\. If changing the mounts, you need to change it as well.

No ill will towards you dude, but we are either having a very hard language barrier issue or you you simply have no idea what you are talking about.

It is not DOSBox config files that we are talking about, it is Theme Hospital's hospital.cfg which tells it where to find the installation within the game's engine

-- edit ---

A bit more clarification in case you are still doubting: the game's executable is running for the OP (maybe you missed that) so the DOSBox config and mounts are just fine. The error about the "CD" is within the game.

Game dont see files in installed path. So ask CD. I understand that, it happen with CD version even after full install (require copy some files from cd and editing cfg file for making game "DRM-free").

It about conf file or conf file(s) - with [autoexec] section. stay hospital.cfg path as c:\ and put text above to autoexec section. Or it just missed space\lines\backslash in cfg and conf files.
Sry for my english.

path=c:\
and
mount C ".." ...
...
and just stay files-folders as in GOG. Installed path not matter (and so - logic drive, PC, or OS - anywhere game can be moved to).

Better move autoexec section from gog's dosboxth_single.conf to main dosboxth.conf file, and then that new conf file move to dosbox-linux executable. I guess it must work same as in Windows...

I understand you, and if the OP was only trying to make one game work, your advice is correct. But, since they have a dosgames directory, I assume their setup is similar to mine and have many games' dirs inside one dir that they mount as C:\

The only thing I know for sure about the OP's setup is that the mounts are not the same as for the GOG install. All the rest, including why they decided to mount the directory differently, are unknowns.

In the case of most games it would not matter, but in TH's case that small modification of hospital.cfg is needed and fixes the issue easily, without needing to go out of the way and changing how the game was configured to run with DOSBox

emm... Still im sure that problem in missed backslash in cfg, or splitting conf file to two as GOG did(*) and missed one of them in start script.
*or just empty autoexec section in conf file - by dosbox default.

I don't know how to say it in another way: The OP decided to mount the game's dir in a different way than GOG's, which they had their reasons to do. And there is no need to mount the game's dir as C:\ as long as you modify hospital.cfg.

In fact, and even if it works for most games, mounting the dirs as C:\ by default as GOG does with many games, instead of a subdir, is bad practice. Installing a game to the root dir of a unit was not commonplace back in the day, and could create any number of unforseen issues.

Bingo, that did it!
Awesome, thanks a bunch. I was thinking way too far into it is all.

Glad to hear it. Enjoy!