OpenWRT supports that.

Though you'll probably end up with Atheros wifi chipset on modern hardware... and I've found the OpenWRT drivers to be extremely unreliable when providing multiple SSIDs--- crashing every few days instead of weeks of uptime.

I keep hoping that one of the OpenWRT snapshots will fix it, but this is something I've been fighting with for years on multiple pieces of hardware.

I bought a Linksys WRT3200ACM specifically for use with OpenWRT after a bunch of research. It's modern hardware and based on Marvell, not Atheros. I don't have lots of SSIDs, but I do have separate 5G and 2.4G SSIDs, and they're working well enough.

Thanks for the info!

Separate 5G and 2.4G SSIDs are no issue in my experience-- it's multiple SSIDs on one phy where Atheros goes wrong.

I really want WiFi6 gear... but given that there's no real OpenWRT support yet, and how long it's taken 802.11ac to mature in OpenWRT (it arguably hasn't yet), it's kind of discouraging.

5G and 2.4G is usually not handled by the same NIC. So that'd be why they're not problematic.

The Velop series, from my own inspection, seems to be based on a custom (neutered) version of OpenWRT

i have had different hardware running openwrt and never experienced problems regarding to multiple ssids...

maybe you have a known-bad hardware in regards to driver support, but that is absolutely not to be expected.

Look at Ruckus

would be good to see more argument behind this?

as the name implies, that company made a ruckus in the prosumer segment like ubiquiti but since bought by Arris is declining same same (like you only get FW updates with registration).

Meraki does multiple wifi SSIDs. Probably does the firewalling too.