Do you have a plan to maintain it long-term or is it just a fork in sake of a fork?
Other than that, for UI/manual testing I'd recommend Restfox or Bruno and ezy for gRPC. Hurl and Step CI for automated testing
Restfox: https://github.com/flawiddsouza/Restfox
Bruno: https://github.com/usebruno/bruno
ezy: https://github.com/getezy/ezy
Step CI: https://github.com/stepci/stepci
Hurl: https://github.com/Orange-OpenSource/hurl
Upd: added links
https://github.com/usebruno/bruno, https://github.com/hoppscotch/hoppscotch, https://github.com/flawiddsouza/Restfox
If you want a more minimal solution/CLI https://github.com/httpie/cli and https://github.com/ducaale/xh work
Restfox [1] has a similar UI to insomnia and works well. Not affiliated with Restfox
Well more than anything, 90% of the use cases are people using it as essentially a GUI CURL. There's countless open source alternatives [1] [2]. They can't ever charge too much money because the space isn't exactly hard to enter.
[1] https://github.com/Kong/insomnia [2] https://github.com/flawiddsouza/Restfox
You can try https://github.com/flawiddsouza/Restfox. It's a web based HTTP client based on Postman and Insomnia.
Disclaimer: I'm the maintainer for it.