I want to use Kodi repository, this one: https://kodi.serialhd.cz/repository.playbe-1.0.0.zip … to play in Plex. Is there a way to convert it to Plex plugin?
(my smart TV doesn’t support Kodi, only Plex)
Simply put, no. Plex is not Kodi. While Kodi can support Plex through DLNA or plugins, the Plex player applications (such as on your Smart TV) don’t have any relation to Kodi.
AFAIK the original Plex Home Theater application was forked from XBMC and theoretically could make use of some XMBC plugins, however that’s all a moot point given that Plex Home Theater is no longer supported, nor does it run on Smart TVs.
It may be possible to rewrite the plugin in a manner that is supported by Plex, however you’d need to know a lot more about Plex plugins than I do, and of course you’d need the source code of the Kodi plugin, along with a fair bit of knowledge. If you didn’t initially write that Kodi plugin I wouldn’t get your hopes up.