I can't install because it has the previous version as a dependency, but I can't install the previous version because it isn't compatible with version 2.x of the game

If its about ltn - port it for private use (or search forks on github, but that could be a violation of the ltn license..)

I also didn't quite understand how to run this mod.
LTN doesn't support 2.0, and I assumed that after installing this mod, LTN would run on 2.0.
What does porting mean?

For example for LTN_Combinator_Modernized thats have no update on mod portal.
On github we have a working (probably) port for 2.0 - https://github.com/cablegunmaster/LTN_Combinator_Modernized read all description (and check other projects of cablegunmaster).

How to install mod from github?
1. Check "Releases" and place mod in the factorio mods folder.
2. Download the project as an archive (Code -> Download ZIP) and extract it to the factorio mods folder.

In truth most all porting activity for LTN to 2.0 has ceased (as far as I know). Optera has explicitly rejected any request to port LTN to 2.0 / Space Age as it is. That is why there is no update from me for LTN_Combinator_Modernized, or LTN Manager from nihilistzsche. Both the LTN Combinator Modernized fork you pointed to, and similarly the LTN one you are probably using are incomplete. Use these things at your own risk, but there are likely things that will not work properly.

And using any port of LTN that you don't do your self is a license violation as Optera does not permit any distribution of modified code.

Yeah, it's a dead project, only for old saves..... no reason to start a new game with it.

Thank you for your answers.