Have you tried connecting third-party levels?
I have so far come to the understanding that in order to add third-party levels to the game, they need to be distributed into folders. In each folder, you need to add a file indicating the order of the levels (first the main ones, then the bonus ones).
Then you need to show this file to the converter and it will recode this group of levels and add it to the game.
I found it inconvenient that there are no instructions. I understood the above by studying my collection of levels from the old version of the game.
But, overall, a decent port. I still hoped that the author of the original game would do something similar. But the author of the original made a re-release only for his shooters. And this game does not exist. So when I accidentally found a mention of this port, it was great.