Hi,
got some money that I could use to buy a router that supports OpenWRT, but can't really decide which one.
We got a FritzBox 7590 right now and a fiber modem. So the router should be at least as good as the 7590 but doesn't need to be a modem.
The router should have a long expected support.
And we still own a landline, so DECT or GAP support would be good.
With the first two points I was thinking about the Flint2, that seems to be a good router with high popularity so should be supported for quite a bit. But it doesn't seem to support DECT/GAP.
There is no support for DECT on OpenWrt, nor on linux in general. You will have to find different accommodations for that (a vendor-supported AVM Fritz!Box running Fritz!OS in client-/ IPoE mode -behind the OpenWrt router- can be that).
Fibre is a wide field, throughputs range from 100 MBit/s to 10 GBit/s, so details are missing.