So I decided to go through with this idea and see how it goes. Here's what I did:

* Started a game in GTAIV Complete Edition on the Steam Deck and created a save;

* Copied the GTAIV folder with its original files & folders, along with my save (found in Documents from wine prefix) from the Deck on to my flashdrive;

* Followed this guide 

on how to downgrade my GTAV:CE copy to 1.0.7.0, to ensure LCPDFR compatibility;

 

* Followed this guide (by the same author) on how to install LCPD:FR Legacy

- I followed those guides to the letter - some files went to /script and others to /GTAIV, I made sure to not have any PDF files where they shouldn't be, and I also made sure to have either xboxliveless or dsound in the folder, and since xboxliveless wasn't there, I kept dsound in /GTAIV. Save files were downgraded to 1.0.7.0, and then I finally edited LCPDFR.ini with the configuration tool. 

 

Upon launching the game, I was greeted by the same text wall the game usually shows, but it got interrupted quickly and then it fades into black, I no longer see the Rockstar or the game logo.

Sound is playing just fine, and then I get to the episode selection screen. No matter which episode I choose, the game will stay stuck at Starting a new game screen. I gave it time, it just won't move forward. I proceeded to remove dsound from /GTAIV, but to no effect, it just won't go past the new game screen. Admittedly those guides are very old (8 years) so I decided to post this thread here, can you help me out? 

 

Thanks in advance.

Did you ever figure this out?