Best setup with a Futro S720, unmanaged switch, and 2 d-link DAP-X1860

I live in relativly large apartment with a lot of concrete. I'm trying to build a budget wifi network with the equipment I have.
I tried to use the DAP-X1860 as extenders but It doesn't work well.
So I thought about building a mesh network and acquired D-Link DIR-X1560 router as it was listed at the DAP-X1860 data sheet as a suitable router to create a mesh network. but it turns out that D-Link is just lying.

I have a futro s720 that I can utlizie as a router.
I have ethernet cables extended to all rooms.
I also have an unmanged siwtch in the box where all the ethernet cables are meeting.
I have the 2 DAP-X1860 "flashed with openwrt"
I have also the DIR-X1560 router but I think it is useless at this point.

Now I'm thinking of building a mesh network with ethernet as backhaul and the futro s720 as the router but I don't know if it is ok or not to connect the DAP-X1860 to it through a switch or not.
I'm looking for suggestion to utilize the hardware I have for the best possible configuration and some high level instructions.

I can also maybe buy other hardware if necessary.

technically, you're not setting up a mesh, if you have wired back haul

Naming has alway been manpulated by companies. But I thought in OpenWRT the wired back haul setup is called mesh as well "I'm not sure anymore".
I'm just looking for best seamless setup I can do with my hardware. I don't care if it is called WDS or mesh.

set up APs where ever you need them, use the same name and password across all radios, should really be enough.

if you want to give them some help, enable 802.11r.

https://openwrt.org/docs/guide-user/network/wifi/wifiextenders/bridgedap

I tried setting up the same name before installing Openwrt and it was a disaster. I will try it again with roaming enabled with openwrt

If you have wired ethernet to all your locations, it's not called 'mesh' (a totally overhyped and wrongly phrase attributed anyways), you have a rather classic setup of a central router and wired APs (https://openwrt.org/docs/guide-user/network/wifi/dumbap), simple - and the best setup possible.

Yes, you can use your unmanaged switch, as long as you don't expect to run (multiple-) VLANs over it; mid- to long term you might want to consider a (smart-)managed switch instead (if you want guest- IoT and other wireless networks as well), but right now the unmanaged switch is transparent to your network and will work.

802.11r is an optimization step, it's not necessary to get your desired setup working, but may improve handover for moving clients (the classic example would be a wirelessly connected SIP phone never losing contact, providing gapless connectivity while you walk through the house). While this sounds nice, quite a few clients don't like 802.11r too much, meaning your results might end up worse than without it - there's no way but trying (in step 2, 3 or 42, not on day 1).