Simulacrius' new infinite research conflicts with other research mods, specifically this one:
https://mods.factorio.com/mod/more-infinite-research
Completely disabling that mod researches

I think for an easy fix it's possible to add an option to disable the Simulacrius' researches in the settings?
Or straight away fixing the issue would be really appreciated

Sorry that I am not sure what do you mean by "Simulacrius' new infinite research".

For researches in this mod, it should have only "rearranged" the research tree by altering some research prerequisites and introduced a new "non-spaceship" recipe for promethium science pack. In other words, it does not introduce new infinite researches.

Could you share more information regarding which exact researches are conflicting and are there any error messages produced?

Oh, that's on me - adding Simulacruis chaned 90% of infinite researches from "More infinite research' mod, and moved to researches I wasn't able to see yet, leaving only couple - I instantly assumed that the ones that are left are from Simulacruis

My bad

So, this "rearranging" also affects the other researches from different mods, not only vanilla. Which isn't, I assume, the point?
Example: I got like, twenty more productivity researches for random things from iron plates to rails, which only takes red and greed science - with Simulacruis it changes to aslo taking chemical and production science. Some others changed into different costs too.

I think it'll be easier if I just provide a screenshot:
https://imgur.com/F3rqnBR

The whole point I'm making - Simulacruis changing research costs of non vanilla mods, and also deleting some researches from other mods, like steel productivity and low density structure from the mod I linked

Oh, that's on me - adding Simulacruis chaned 90% of infinite researches from "More infinite research' mod, and moved to researches I wasn't able to see yet, leaving only couple - I instantly assumed that the ones that are left are from Simulacruis

My bad

So, this "rearranging" also affects the other researches from different mods, not only vanilla. Which isn't, I assume, the point?
Example: I got like, twenty more productivity researches for random things from iron plates to rails, which only takes red and greed science - with Simulacruis it changes to aslo taking chemical and production science. Some others changed into different costs too.

I think it'll be easier if I just provide a screenshot:
https://imgur.com/F3rqnBR

The whole point I'm making - Simulacruis changing research costs of non vanilla mods, and also deleting some researches from other mods, like steel productivity and low density structure from the mod I linked

As for errors - only one I got after adding Simulacruis is this one:
https://imgur.com/a/n0Bp58O#Xf2tPZM

Thank you for the screenshots.

Here is what I found after looking at the screenshots:
- There are 3 more infinite researches on the right hand side (without Simulacruis)
- The icons of the 3 researches seems to be LDS, blue chips and steel , which are 3 of the default Factorio ones and they are also shown in the 2nd screenshot of the mod message.
- Interestingly, I also see the research science pack requirements are different from left hand side and right hand side. For example, belts require 5 science pack on the left hand side while it only requires 2 from the right hand side.

I have also installed the MIR mod and checked that there are no differences in the available inf. technologies with or without Simulacruis.

Combining with the message from the mod dialogue box, it seems that you may have installed other mods as well. I suspect that may also contribute to the issue. Could you try to compare from your end if the technologies are different with Simulacruis installed, but comparing if other mods being enabled vs disabled? A new sandbox save with all research completed could be used to tell the inf. researches apart.

I have also installed the MIR mod and checked that there are no differences in the available inf. technologies with or without Simulacruis.

That's odd, that previous comparison screenshot was made only using two mods - Simulacruis and MIR, aside from base game mods, like space age and quality:
https://imgur.com/avZa2aG

In a fresly made save file (all researches are red)
Last game version, not in experimental

Removing the Simulacrius mod from the test world results in this message,
https://imgur.com/a/Ms1XN8b
As well as the cost change of researches back to using only red and green science, like on the previous screenshot I've sent

So, apparently, clicking the "update" button in the mod menu fixed the issue with the research costs...
At least most of it, just couple techs have increased research costs but not drastically, like thruster fuel tech taking agriculture packs now
It was on the MIR side probably, since I saw it being updated

I feel kinda dumb now

Though, error pop out with the removed tech persists:
https://imgur.com/a/NKRdFjk

Which weirds me out, since inserter capacity 8 doesn't exists in both with or without Simulacrius mod, as well as cannon and electric shooting speed tech
Laser shooting speed, research speed, weapon shooting speed, and worker robots storage still exists in the same level and research cost in both as well, perhaps research IDs got changed

Anyway, I'd consider the issue... solved. Thank you for your attention.

Happy for you to find the solution. If you have further problems with MIR, I would suggest you to contact their author to see if they could share more on it. Good luck.