[2023] Steam runtime communication error after verifying files' integrity.

Does that Steam verify process find anything to fix?

If so, my guess is one or more of your mods is (incorrectly) putting or changing files in the game's folder, instead of the mod folder.  

I don't know then. You should be on launcher 2023.1.1 now, is that right?

If so, Please try the following:

- unsubscribe from all mods in BOTH the Steam Workshop and the Paradox mod site mods.paradoxplaza.com
- delete the folder Documents/Paradox Interactive/Stellaris/mod/
- delete the file Documents/Paradox Interactive/Stellaris/mods_registry.json (if present)
- delete the file Documents/Paradox Interactive/Stellaris/launcher-v2.sqlite (if present)
- run the game up and check the launcher is okay with no mod or other errors
- subscribe to a few mods

- run the game up and see if those mods are now available to you.

I hope that does it for you!  

Probably time to employ the thermo-nuclear option then, I'm sorry!

- move any valued save games elsewhere, and user empire designs.txt from /Documents/Paradox Interactive/Stellaris/ if you have made any custom empires or races.
- "uninstall" in Steam-Stellaris
- exit the Steam app entirely
- manually delete both the Steam/SteamApps/common/Stellaris AND Documents/Paradox Interactive/Stellaris folders
- delete everything in the Steam folder EXCEPT steam.exe and the SteamApps folder
- run steam.exe to rebuild all that
- re-install game in Steam, run a Steam Verify when done.
- add stellaris.exe to the exceptions list of your antivirus app; ESPECIALLY if you have Windows Defender, add it to the Ransomware "Apps Allowed Through" list.
- start the game with no mods active and test
- now try the mods

Good luck!  

I don't know then.

What if you make a new Windows user on this machine and log into it with that?  

Then either there are still game, mod or launcher files left in your original Windows user profile folders, OR that profile is bugged or corrupted in some way.

I can't think of anything else that could cause this to you!  

I don't know how this problem could occur as you describe in one Window user profile but not another, unless there are still some game, mod or launcher files left in your original Windows user profile folders.