Fixed IP address for Home assistant

Exactly. You use a second party router which I said is likely the only solution for (at least) my issues.
You know of course that if I implement a second party router I have essentially disable the “router” part of the Starlink of implement the second router on a second VLAN because I cannot have 2 DHCP servers in the same network.

I have several routers around, older, but I could alway DDWRT them if supported. I guess time to bite the bullet and do it.

The simple point I was making is that the solution is dependent on many factors and assuming fixed vs DHCP is not just a simple decision, get all the facts before you impart opinions.

Run router software and bridge the ISP router.