I am commercial software developer, and my piece of software dynamically calls the LGPL v2.1/LGPL v3 library. Am I allowed to notarize my installation package that includes LGPL dynamic loaded library binary? Addidional Option b) To protect my software from replacing dynamic loaded library with some malicious code is it allowed with LGPL to verify library code sign? Veryfing checksum I believe is strictly not allowed with LGPL.
The LGPL v3, Section 4(d)(1)(b) requires that your program
will operate properly with a modified version of the Library that is interface-compatible with the Linked Version.
(Very similar language exists in Section 6(b)(2) of the LGPL v2.1)
Verifying the checksum of the library will mean your program will not operate properly, so you are correct you are not allowed to do this; the LGPL is explicitly designed to allow users to replace the LGPL code when it is combined into a larger work.
The details of notarization are not entirely clear to me but the same principle applies: the user must be able to replace the LGPL code with an interface-compatible version and still run the software (and in the case of LGPL v3 software, still install the software as well). If as you say in comments it is possible to enable this with one simple command, I believe that would be acceptable.