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It really depends how you define reliability. SD cards are physically nigh indestructible, but can show failure when overwritten often. Hence for one off backups it’s actually a good alternative. It will start showing problems when used as a medium that often writes and overwrites the same data often.
I would recommend backups on SD cards in an A/B fashion when you want to give a backup to someone else to store safely.
Adding to that that you can also easily make a separate WiFi network (tied to a vlan even) for IoT. OpenWRT makes this very easy.