So finally I got to a J2300 router (running junos-jseries 9.3R4), and could not upgrade it...
lab@J2300>request system software add /var/tmp/junos-jsr-9.5R3.7-domestic.tgz no-validate
Installing package '/var/tmp/junos-jsr-9.5R3.7-domestic.tgz' ... Verified junos-boot-jsr-9.5R3.7.tgz signed by PackageProduction_9_5_0 Verified junos-jsr-9.5R3.7-domestic signed by PackageProduction_9_5_0 ERROR: Unsupported platform j2300 for JUNOS JS, use a jseries package ERROR: junos-9.5R3.7-domestic fails requirements check
Best Regards, Petr (PK)
Juniper Ambassador, Juniper Networks Certified Instructor, JNCIE-SEC #98, JNCIE-ENT #393, JNCIE-SP #2253 [Juniper Authorized Education & Support in Russia]