Chinese hackers hacking Ukrainian infrastructure, starting during the winter olympics and continuing until the day before the invasion.
I hate to break it to you, but hacking goes on between nations at the best of times, and between nations that are outwardly friendly to one another. Regardless of whether it's something designed to be a nuisance (DDoS for example) or something targeted and designed to do more damage, it happens. It's also not illegal in the way that supplying weapons is. Naughty yes, but nothing you can really get anything done about.
Can you also conclusively prove it was conducted with the
backing of Chinese authorities? It's probable that the authorities knew what was going on, but didn't get involved because the hackers weren't bothering with local systems. The hackers may have had backing, but you'll never be able to prove it conclusively. Saying something bears all the hallmarks of being something is not the same as saying it definitely is.
1. The fact that you can't entirely eliminate Chinese products from your life doesn't mean you can't eliminate as many as possible.
2. One aspect of a boycott that is sometimes forgotten: making sure suppliers know why you made particular choices. For instance, you can email suppliers to determine the provenance of products you're considering, and when they respond, make it clear that you've decided to avoid X because it's made in China (and give the reason – Uyghur genocide, support for Ukraine, etc).
1: There becomes a point where it's no longer practicable whether for physical or financial reasons. I'm not going to start checking and sourcing where all my products come from because I'd probably never buy anything again. I spend a lot of money on tech, and considering a lot of chips and chipsets are produced in China there's nothing I can do. Sometimes there are alternatives, but they'll be a lot more expensive, and as I'll usually buy 7 or 8 at a time it's already expensive. Am I going to pay £2000 for 8 motherboards, or £3000 just to make a point?
2: Suppliers don't care about people e-mailing them and telling them their world views. At any given time, people will refuse to buy any product for whatever reason, be it it doesn't taste nice or because it's made from the blood of new-borns. For every person who mails them, there will be 100 people who buy the product because they simply don't care, and have more important things to worry about.
It all goes back to what I said about convenience. I've donated money, a large amount of digital tokens that have monetary value, and bought a few Ukraine software bundles. The reason was basic convenience. I've got my own problems going on, and unfortunately they haven't decided to lay off because of Russia invading Ukraine. By doing what I did, I got a warm fuzzy feeling from doing something nice, and then went and dealt with stuff that has real world consequences if ignored. I don't have the time to research where individual things come from. There are things I won't buy because I've been made aware of a reason, but it has to be a lot better than a country remaining neutral.