The Cybersecurity and Infrastructure Security Agency (CISA) publishes information and updates on the Ukraine/Russia situation on their Shields Up site:

https://www.cisa.gov/shields-up

CISA/USCERT threat overview and advisory round up for Russia's cyber capabilities:

https://www.cisa.gov/uscert/russia

One of the most important things to do is prepare. CISA's database of vulnerabilities that are known to be exploited in the wild can help determine what applications to pay most attention to when patching:

https://www.cisa.gov/known-exploited-vulnerabilities-catalog

President Biden's March 21 statement on the Nation's cybersecurity:

https://www.whitehouse.gov/briefing-room/statements-releases/2022/03/21/statement-by-president-biden-on-our-nations-cybersecurity/

The White House also release a Fact Sheet along with the President's statement:

https://www.whitehouse.gov/briefing-room/statements-releases/2022/03/21/fact-sheet-act-now-to-protect-against-potential-cyberattacks/

The Federal Trade Commission (FTC) and many news outlets have run stories on avoiding fundraising scams in reaction to an increase in Ukraine aid themed phishing attacks:

https://consumer.ftc.gov/consumer-alerts/2022/03/donating-crypto-watch-out-scams

https://www.cnbc.com/2022/03/01/russia-ukraine-crisis-how-to-avoid-fundraising-scams.html

https://www.bbc.com/news/technology-60836962