My stellarmate hotspot doesn't have the coverage I need and for several reasons I cannot use a direct ethernet connection to my PC.
To solve this problem, I'm trying to connect my stellarmate to a wifi router via ethernet cable.
This way I could move the router a little closer to my room.
I also hope that the router has a greater range than the raspberry antenna.
This way I would have a good signal to connect wirelessly from my PC (with VNC).

I have a TP-link router connected through the WAN port to the raspberry ethernet port.
I selected the ethernet connection in network manager.
I have wifi signal; I can connect to the router but I cannot connect to stellarmate.
From here I'm lost and I need help.

I remember reading in the forum that some people are using this same system.
I would be grateful if someone could pass me some guidelines, hints or links to help me.

So connection to router via Ethernet is supported out of the box no configuration needed. Try to go to your router settings and check for connected clients and check the IP address assigned to StellarMate.

Ideally, you can reach stellarmate via stellarmate.local name but in case the router has issues, it's better to connect to StellarMate using the IP address directly.