Tockify looks like one of the few solutions that would work that has a free version. I've never used it, but it's mentioned in a few "embeddable calendars" articles. Source: almost 2 years ago

You can change the colors a bit, but that's about it. To do anything more you need an integration code and things won't look good on mobile without more coding help. There are options like tockify.com and http://upto.com/ that will do this all for you, but they cost money. Source: almost 2 years ago

Onin | London, UK or similar timezone | REMOTE | React Native, Swift, Objective-C | £120K and £100K options + Private Health Insurance + 33 days holiday (incl. Bank holidays) The app: https://onin.co With a founding team of just two we closed a seed round of £2.75M in July 2022. We’ve since hired two engineers. We plan on keeping the engineering team as small as possible with a highly selective hiring process. Our... - Source: Hacker News / over 1 year ago

Hey, it’s Ryan here (co-founder of YC-backed Muzz, the world's largest Muslim dating app). I’m now building Onin, an end-to-end encrypted (E2EE) calendar and chat app that makes organising your personal and social life simple and secure. Source: over 1 year ago