Hard to say without knowing which method you used to install HomeAssistant.

But I never found mdns .local addresses to be very reliable. They work 80-90% of the time, but the remaining 10-20% are a hassle.

Instead I’d recommend you install PiHole (in a docker container is easiest). PiHole is a DNS server intended for network-level ad-blocking. But it also have a handy feature of defining local DNS entries, so you can have HomeAssistant.myhome or HomeAssistant.whatever (.local should not be used with PiHole local DNS because .local is meant for mdns)

Not Op, but I was in a very similar situation (decent pay, old house, old car, not many fancy purchases). While many people here will borrow a lot and pay the minimum on their mortgage, I paid down my mortgage completely. (and otherwise spent money on travel).

Ironically, this is bad financial advice. The last 15-20 years interest have been very low, and house prices have soared. It would make much more financial sense to borrow more and buy a nicer house. But I value the freedom I get from not having a mortgage. And I never borrowed to buy a car, as cars depreciate like rocks