California's actual website for filing corporate documents
cafile.sos.ca.gov
cafile.sos.ca.gov
It has a valid TLS certificate, provides a free service, renders in modern browsers, and there's a reasonable chance it's been working fine for both the CA SoS and lobbyists given that it hasn't required many updates.
Stability and durability could be very good signs for software which keeps a paper trail regarding democratic processes. Use of trendy or as-yet-unproven technology from within the past few years would be more notable as a red flag.