Router for good wifi range

My current setup is a D7000 modem/router and EX700 mesh extender. The D7000 seems to be getting a bit tired, needing to be rebooted every week or so so it is probably time to replace it.

I have around 40 devices connected (lots of 2.4 GHz IOT things), and sync at around 65 Mbps FTTC.

I don't need a super high performance router (although there are 3 people WFH now), good range is probably my most important requirement since its an old house with real walls.

I'm not sure if WiFi 6 provides anything useful in my situation (with few particularly new endpoints today) - or if a stand-alone modem is a sensible choice to add a bit of flexibility?

Any suggestions for good or bad hardware? Budget is flexible...