How to promote a Chrome extension?

This is actually useful for hotels/hostels in the remote locations, you should try selling it to them for a monthly small fee to put it up once the COVID-19 situation comes down, people will travel like crazy then.

A few things you could do to share your product:

1. Post about it in niche communities on Facebook, Reddit, etc.
2. There are many prompts here showing up regularly, where you could share your product in replies.
3. You could do the same by replying to people tweeting about travel.

About the paid channels, newsletters are a great way to reach an engaged audience. Many newsletters are also running discounts on their sponsorships. I've also got a 50% off offer for indie makers on Product Disrupt Newsletter.