A lot of very useful software is not multithreaded. Hell, javascript is not multi-threaded.

What I know is that I have vastly more compute and disk at home than I can afford to run in any cloud. So it seems a shame to not use it - perhaps with a cloud front end and secured connection to the home equipment.

If you guard the machine well via firewall you can simply Let’s Encrypt for SSL via AAAA records to the public IPV6 address of one of your home machines with nginx reverse proxy.

A 4090 is good enough for running many models. You probably want an A6000 for larger ones. But many models that don’t fit in your VRAM can be scaled down without much loss of effectiveness.