The default DHCP lease in the Asus is 24 hours.

Could it be simply renewing the IP address for each machine?

If you're on Comcast / Xfinity, and if you're in one of their "enhanced" service markets, then you might want to consider the Hitron Coda56 modem, which is on their approved list for faster upload speeds. If not, the S33 is perfectly acceptable.

Yes.

On the switch, define the ports that need to be on VLAN2 as "access ports".

VLAN2, Untagged, PVID2

Then use a single cable from your edgerouter to any one of those ports.

Make sure that no other (V)LANs are assigned to that particular port on the EdgeRouter.

Yes, this is fairly common behavior.

Cheap routers such as Linksys and NetGear often have a hard time re-establishing the WAN connection when the cable modem is power-cycled.

You could try going into your Linksys, and manually setting up to WAN connection. If the Arris IP is 192.168.0.1 for example, manually set your WAN connection to something like this:

192.168.0.2 Mask 255.255.255.0 Gateway 192.168.0.1

Save your settings, and restart both devices.

What ISP speeds will you be dealing with?

Do you actually need 24 ports?

How many access points will you be using?

2" minimum separation between ordinary electrical wiring, and communication cables. At least that is code here in the US.

6-8 inch separation is usually preferred for long, parallel runs.

From your photos, you shouldn't have any trouble.

The most affordable WiFi router (that I'm aware of) that supports VLANs right out of the box is the GrandStream GWN7062, currently listing at $187 CAD on Amazon. It can be meshed with other GrandStream devices.

It's probably not as flexible as the ER-X, but should be able to handle all of the basics.

Another possibility is the Synology MR2200ac.

Powerline is hit or miss.

Either it will work well, or it won't work well at all.

For folks that can't escape Powerline, I typically steer them to units that utilize the newer G.hn technology, such as the Zyxel PLA6456

If the room with the router and the room with your PC are on the same circuit breaker, you'll probably exceed 400Mb speeds.

I'd be way more prone to just drilling the 1/2" holes through the two walls just above baseboard level, and running a cable. No plug-and-pray, and no doubts about whether you're getting the best connectivity to your router.

A switch port port can support the following:

1 or more Tagged VLANS

1 Untagged VLAN by itself

1 Untagged VLAN plus one or more Tagged VLANs

A switch port CANNOT support more than one Untagged VLAN.

In all of your pictures, port 4 is correct.

In the 2nd picture - you'll note that the VLAN60 and 61 boxes are red. That's because you've selected Untagged VLAN60 and Untagged VLAN61 on ports 1, 2, 3, and 5. That isn't a valid configuration.

Your first picture has VLAN60 set for untagged traffic on ports 1, 2, 3, and 5. . . anything plugged in to those ports would be dumped onto VLAN60 during normal operation.

If you want VLAN61 as untagged on ports 1, 2, 3, and 5, you'd change the VLAN60 entries on ports 1,2, 3, and 5 to "E", and then in the VLAN61 row, change 1, 2, 3, and 5 to "U".

So, top row correct for VLAN60, middle row completely invalid, and bottom row won't put any VLANs on ports 1, 2, 3, and 5.

If you have a spare coax cable that you can use for testing (even if it is a short one), try swapping it out, and see if your blue lights come back on.

I've had borderline / intermittent coax cables in the past.

They make these for 6 cables. . .

https://www.ebay.com/itm/285197205528

Single screw in the middle holds them down. . .

If you want the AC88U to actually "route" traffic, then set your AT&T router to "bridge mode". There's probably tons of instructions online as to how to accomplish that.

If you don't bridge the AT&T modem, you'll end up behind two layers of NAT, which can cause problems with gaming and port-forwarding.