When buying a PoE switch, I decided to make a compromise: I bought a switch without smart managed support features, hence that means no VLANs. Nevertheless, I persist to ask the question. Can you use VLANs with an unmanaged switch? The answer is yes! Sometimes. How does this work? Basically, forwarding and switching Ethernet packets depends only the source and destination addresses. The switch can use broadcast testing followed by storing into a MAC address table to determine this without any VLAN knowledge. Only the end devices need to have VLAN capabilities, and so long as tagging is used for all VLAN packets, it will all work out just like so.
When might this not work? Some ASIC chipsets are unnecessarily strict in checking packet CRCs and will thus fail on any VLAN tagged packet. Suffice it to say, generally speaking newer ASIC chips will be gracefully designed to handle VLAN tagged packets, but older ones will be unnecessarily stringent.
20200105/DuckDuckGo can an unmanaged switch forward vlan tagged packets
20200105/https://community.netgear.com/t5/Unmanaged-Switches/ingress-tagged-traffic-on-unmanaged-switch/td-p/1122243
20200105/https://serverfault.com/questions/333859/what-happens-when-a-consumer-switch-receives-a-vlan-tagged-ethernet-frame