Thank you for your recommendation. After reading the post related with aht79 tiny, it seems to be a good alternative to re-purpose unused old hardware for range extension (not routing).
If you plan to buy a new device, the wiki documentation discourages to buy 4/32MB devices (as @tmomas had already pointed out).
Someone else is looking for a replacement for those old and trusty tplink tl-wdr4300 tl-wdr3600 and tl-wdr3500 (this last one without gigabit ethernet ports)? For a small router, Netgear WNDR3700v4 (whenever a used unit it might be available) and TP-Link Archer C7 AC1750 seem to be valid alternatives, gigabit ethernet 1xWAN, 4xLAN, and decent amounts of memory for the firmware and RAM.