Dear Radosław,
Please note that the way Webbrewers provided isn't supported in the general modern sites (the modern group-connected sites).
Not sure what you mean by that-we still use list templates in modern sites regularly. It would be ridiculous to block that functionality in "modern group sites" but not other site types given the complete mess Msft has made with their confusing naming habits. Very few people know what a "modern group-connected site" even is. And if what you say is true, the option to create list templates should be removed. Leaving functionality out there that may or may not work with a site is a very amateurish approach and just exacerbates the confusion that surrounds Sharepoint. Another example of Msft's careless and sloppy management of the platform.