Rhasspy. Idk if rhasspy3 is out fully, but I would wait for that and then set it up. (I have began to see the home assistant side being released - its supposed to tie in a lot better than rhasspy2, and even brought the dev on to the HA project)

Old PC that can be on all the time.

If you dont have one and want dedicated hardware, I would recommend a used server, or something you can whitebox (like using as asrock rack mobo that takes a desktop ryzen but supports ecc memory)

Put proxmox on as the host OS, two ssd’s in raid 1 is good for a boot drive / VM storage drive. Raid 10 if you want real high performance, but probably unneeded.

Look for a case that has a SAS backplane, and then connect the backplane to a HBA card. Pass this card through to freenas for storage shares and stuff.

I recommend not virtualizing your router. So, if you want togoet away from Soho gear, either flash a Soho router with openWRT, or build a separate box for pfsense or opnsense. If you go that route, you will need a separate switch / access point. Unifi gear has a good balance of features and affordability, and can all be managed from a single ui (let’s say you have 3 switches and 2 access points… You dont need to go to 5 web UI’s, its all in one spot - and you can self host the web ui in proxmox)