Alaska

https://voterregistration.alaska.gov/

Texas

Print the generated PDF and physically mail. Sorry.

https://vrrequest.sos.texas.gov/VoterApplication/ConfirmStatusEN

Idaho

https://votertools.voteidaho.gov/electionlink/electionlink/ApplicationInstructions.aspx

California

https://covr.sos.ca.gov/

Washington state

Verify automatic registration (jealous!)

https://voter.votewa.gov/portal2023/login.aspx

Oregon

https://secure.sos.state.or.us/orestar/vr/register.do?lang=eng&source=SOS