Forum Discussion
The solution about SAN that does not indicates any limitation:
https://support.f5.com/kb/en-us/solutions/public/13000/400/sol13470.html
Also, the RFC does not define a limit:
https://tools.ietf.org/html/rfc5280
" SubjectAltName ::= GeneralNames
GeneralNames ::= SEQUENCE SIZE (1..MAX) OF GeneralName"
"The construct "SEQUENCE SIZE (1..MAX) OF" appears in several ASN.1 constructs. A valid ASN.1 sequence will have zero or more entries. The SIZE (1..MAX) construct constrains the sequence to have at least one entry. MAX indicates that the upper bound is unspecified. Implementations are free to choose an upper bound that suits their environment."
The implementation of the protocol may or may not limit that. However, you will be limited by other protocols limitation, as TLS is limited for example.
https://tools.ietf.org/html/rfc5246section-6.2
"length The length (in bytes) of the following TLSPlaintext.fragment. The length MUST NOT exceed 2^14."