

You can create a virtual machine, running within your debian install, to serve as your router. It actually works very well.
I used a headless Debian VM as a router with Shorewall to configure iptables. If I had to do it again, I probably would have used an opensense VM.
Check permissions on your home folder. Make sure everything is owned by your new username.
I had a separate partition mounted on /home on my old system. I remounted the same partition at /home on the new system, and got the same bootloop issue. The problem was that the old permissions were for 1001:1001, not (newuser):(newuser). Had to log into a TTY and chown (newuser):(newuser) -R /home/(newuser) to get everything working.