https://www.gnu.org/licenses/gpl-faq.en.html#GPLPlugins
> If the main program dynamically links plug-ins, and they make function calls to each other and share data structures, we believe they form a single combined program, which must be treated as an extension of both the main program and the plug-ins.
That scenario is not a good fit for LGPL.
https://www.gnu.org/licenses/gpl-faq.en.html#GPLPlugins
> It depends on how the main program invokes its plug-ins. If the main program uses fork and exec to invoke plug-ins, and they establish intimate communication by sharing complex data structures, or shipping complex data structures back and forth, that can make them one single combined program. A main program that uses simple fork and exec to invoke plug-ins and does not establish intimate communication between them results in the plug-ins being a separate program.
> If the main program dynamically links plug-ins, and they make function calls to each other and share data structures, we believe they form a single combined program, which must be treated as an extension of both the main program and the plug-ins. If the main program dynamically links plug-ins, but the communication between them is limited to invoking the ‘main’ function of the plug-in with some options and waiting for it to return, that is a borderline case.
No company should ever do business under terms that are this unclear. It's just asking for trouble. Use another licence that is not this ambiguous.
The important part is that you should be able to modify the LGPL library that the application uses. In the case of a python module or plugins, it is possible, so that's ok for LGPL. You can even statically link LGPL libraries with your proprietary application as long as you provide a way to relink your application with a modified version of these libraries.