Selfhosted

You need a wifi router. Connect the wan to your network. One mac, wan doesn't know about your devices.

I used a GL.iNet Opal to do exactly this while travelling.

May I ask is that a new way of leeching $ from people? Or is there a good reason to charge for each MAC?

I don't know if this applies to all phones, but my Android phone can act as hotspot while connected to a regular AP, and it does NAT so it appears as one device

Isn't "MAC NAT" you are after? I've seen Mikrotik has this feature to perform NAT for bridge devices. EDIT: no, since your ISP might check at DHCP leases and realise that you are cheating. Go with regular router instead.

Also regular router would be sufficient IMO. Also don't forget to set static TTL value so your "ISP" doesn't see that you have a router between your devices.

Also create MAC address and save it. Always change it before connecting - you will have less trouble.

@aboringdystopia

Am I missing something here or can you just use any hotspot capable Smartphone for that?

I think openwrt can do that. You would just put one of the radios (2.4 or 5ghz) into WAN, and the other into LAN.

Obviously that limits you to 2.4ghz speeds, if you want faster two routers back to back could maybe work.

To my understanding, a network switch will relay your MAC address, so it’s sounding like that is what your range extender is. You would need an actual wireless router. You could get a wireless mesh router pair, so you have both a new wifi and range extending. I’d then disable the wifi on your main router. It sounds like they make you use your ISP’s router, but it’s also worth trying to disconnect that and plugging your new router direct into the modem instead to see if you need the ISP router at all. Also, you’d need to whitelist the new device with the ISP.

I would recommend getting a separate client radio device for several reasons:

• You can position it better for reception
• Get a device with directional antenna so you can point it at the best AP
• You won't use up 1 band of a dual-band router
• You won't be limited in your main router firmware choice to only those that support client mode on a radio

Personally I would get a nanostation loco 5ac (non-loco is bigger and probably isnt needed) and flash openwrt on it (that will free any airmax radio from the proprietary airmax limitation), configure the 5GHz radio to client mode with the apartment wifi details, and put in the desired mac into the mac field if you need a specific mac besides the device default. Make sure the radio is set to wan zone so that forwarding works and plug the lan cable from the radio to the WAN of whatever nice router you have.

I used to carry around a nanostation with this config set to xfinity access points with a small script that would pick a random MAC from a list I gathered from wardriving client MACs that I saw authenticated with xfinity hotspots. That way if I ever needed an ethernet connection for a non-wifi device I could just power up the radio and run the script to pick a new mac until I got one that was "remembered" in someone's xfinity account.

Edit: to clarify, I think the way I set it up was to run dhcp client on the radio's uplink and then hand out IPs via dhcp server on the lan port, so I think you'd be triple natted, but since you would need to double nat anyway to get around the MAC authorization it probably isn't hurting speeds any more than it already would be.