Switch from your work computer to your own computer. If you don't have on the clock vs. off the clock, then I think you could make the argument that you were doing work stuff and then moved to your own computer to do your own stuff.

At work computer versus at own. Or even VPN on, versus off VPN, though that’s harder if you don’t use one.

Even accounts could be a reasonable separation.

If you absolutely had to use your personal computer for a full time gig I can’t imagine how having a clean slate and user namespace wouldn’t be beneficial.

Discreet SSH keys, directories, downloads, etc.

I work from home and even when I have no startup plans I still keep two separate browser profiles, ssh keys, directories etc, exactly for the benefits you mentioned. Things like autocomplete suddenly become "smarter" if they know I'm looking for something work related.

I have two accounts on my home workstation to create a separation.

10+ years freelancer. I have virtual machines for each client, and a personal one where i test my stuff. Currently ~10 machines sitting on my PC hard, plus 20+ backed up on a separate backup hdd specially made for this. And all are backed also in the cloud, on encrypted volumes, under different providers with thousands of accounts each, all managed by a password manager (I made my own pwd manager for my own needs).

This setup allows me full separation for each client plus my own stuff. Personally I think this is the best solution. Only downside is that requires a good internet connection, which in my country is a non-issue